Login Troubleshooting - Openproject

If you’re having trouble logging into the OpenProject Mobile App, the following sections will help you identify and resolve the most common issues.

Invalid or Inaccessible Instance URL

Symptom:
You see a browser error such as “The site can't be reached. The server address could not be found”.

Possible cause:
The URL you entered may be incorrect, inaccessible, or not using HTTPS.

Possible Solution:

Double-check the URL format (e.g., https://yourcompany.openproject.com).
Ensure your instance is publicly accessible and uses HTTPS (HTTP is not supported).
Try opening the same URL in your mobile browser to confirm connectivity.

OAuth Application Not Enabled

Symptom:
Login fails with a browser error such as _“An authorization error has occurred. The client is not authorized to perform this request using this method.”, or you are redirected back to the login screen without authentication.

Possible cause:
The mobile app uses OAuth 2.0 for secure authentication. If the built-in OAuth applications are not enabled in your instance, the app cannot log you in.

Possible Solution:

Go to your OpenProject administration area at:
{BASE_URL}/admin/oauth/applications
Make sure that Built-in OAuth applications are enabled.
If you don’t have admin rights, contact your OpenProject administrator.

TLS error in the app but the site opens in a browser (incomplete certificate chain)

Symptom:
You cannot sign in to the mobile app against a self-hosted OpenProject instance. The app reports a TLS/certificate verification error or a generic “Unable to sign in” message, even though the OpenProject URL opens normally in a web browser.

Possible cause:
Your server is serving an incomplete TLS certificate chain, only the server (leaf) certificate, without the intermediate CA certificate(s) needed to link it to a trusted root.

Browsers often hide this issue because they can download missing intermediate certificates automatically (AIA fetching) or reuse cached intermediates. Mobile app HTTP clients typically require the server to present the full chain during the TLS handshake, so the same server can work in a browser but fail in the app. This is a server configuration issue.

How to confirm:

Online: Run the SSL Labs Server Test: https://www.ssllabs.com/ssltest/analyze.html?d=YOUR_INSTANCE_DOMAIN. If you see “Chain issues: Incomplete”, this is likely the cause.
Command line: openssl s_client -connect your-server.com:443 -servername your-server.com </dev/null. In the output, check the Certificate chain section. If it lists only entry 0 (the leaf certificate) with no intermediate entries (1, 2, …), or you see: Verify return code: 21 (unable to verify the first certificate), then the chain is incomplete.

Possible Solution: Configure your web server/proxy to serve the full certificate chain (leaf certificate followed by the intermediate certificate(s)):

nginx: ensure ssl_certificate points to a full-chain bundle, not a leaf-only file. For example: cat your_domain.crt intermediate.crt > fullchain.crt
Let’s Encrypt/Certbot: use fullchain.pem, not cert.pem.
Apache: provide the intermediate certificate(s) via SSLCertificateFile (bundle) or SSLCertificateChainFile (older setups).
Load balancer/reverse proxy/CDN (AWS ALB, HAProxy, Cloudflare, IIS, …): make sure the intermediate certificate field is not empty.

After updating the configuration, re-run the SSL Labs test to confirm the chain issue is resolved, then try signing in again from the app.

Instance Not on Minimum Supported Version

Symptom:
You know that your instance is running not on the minimum supported version, OpenProject 17.0.0, and the login fails with a browser error such as “An authorization error has occurred. The client is not authorized to perform this request using this method.”.

Possible cause:
The OpenProject Mobile App requires your instance to be on OpenProject version 17.0.0 or higher.
If your instance is running an older version, OAuth authentication may be disabled by default.

Possible Solution:

Ask your OpenProject administrator to check the current version of your instance.
Update to newer version of OpenProject.
- If updating is not am option, the administrator can temporarily enable OAuth authentication by removing the feature flag under: {BASE_URL}/admin/settings/experimental
- Once this flag is removed, the built-in OAuth applications will be available in {BASE_URL}/admin/oauth/applications, once enabled the users can log in via the mobile app.

[!NOTE] Upgrading to the latest OpenProject version is recommended for the best compatibility and security.

Invalid SSL Certificate

Symptom:
You receive a browser error message such as “Secure connection failed. Untrusted certificate”.

Possible cause:
Your OpenProject instance must use a valid, signed SSL certificate (HTTPS). Self-signed certificates or expired certificates are not supported.

Possible Solution:

Verify that your SSL certificate is valid and trusted by your device.
If you’re using a self-signed certificate, replace it with one from a trusted certificate authority (CA).

Wrong Credentials

Symptom:
You see “Invalid username or password” when logging in.

Possible cause:
Your login credentials are incorrect or have been changed.

Possible Solution:

Make sure you’re using your OpenProject account credentials, not your email alias (unless configured as your username).
Try logging in via the web version of OpenProject to confirm your credentials.
Reset your password if necessary.

On-Premises API Access Disabled

Symptom:
Login attempts fail with no clear error message.

Possible cause:
Your on-premises OpenProject instance may have API access disabled, preventing the mobile app from connecting.

Possible Solution:

Log in as an administrator and navigate to:
Administration → System settings → API
Ensure that API access is enabled.
Save changes and try logging in again.

Instance Using HTTP Instead of HTTPS

Symptom:
You receive a browser error message such as “Secure connection failed. Untrusted certificate”.

Possible cause:
The mobile app only supports secure connections via HTTPS.

Possible Solution:

Configure your instance to use HTTPS with a valid certificate.
Redirect HTTP traffic to HTTPS using your web server configuration.

Firewall or Network Restrictions

Symptom:
Login attempts time out or fail when using certain networks with an error such as “Login time out. Check your network”.

Possible cause:
Corporate or restricted networks may block outbound requests to your OpenProject instance or authentication endpoints.

Possible Solution:

Check the network connection of your device. Internet access is required for the app to work.
Try connecting from a different network (e.g., mobile data).
Ask your IT team to whitelist your OpenProject domain.