UPGRADE.md
If you have 1.5.x and want to upgrade to 3.0.x, You may try to contact our dedicated support
BACKUP YOUR EXISTING STORE FILES AND DATABASE!!
Admin -> System -> tools -> BackupDownload the latest version of OpenCart and upload all new files on top of your current install except your config.php and admin/config.php.
Browse to http://<yourstore.com>/install Replacing <yourstore.com> with your actual site (and subdirectory if applicable).
You should see the OpenCart Upgrade script.
config.php files. Restore them from your backup first. Then try again.Click "Upgrade". After a few seconds you should see the upgrade success page.
Clear any cookies in your browser
Goto the admin side of your store and press Ctrl+F5 or Ctrl+Shift+R for several times to refresh your browser cache. That will prevent oddly shifted elements due to stylesheet changes. Login to your admin as the main administrator.
Goto Admin -> Users -> User Groups and Edit the Top Administrator group. Check All boxes.
Goto Admin -> Extensions -> Extensions -> Theme enabled and save the default theme again.
Goto Admin -> System Settings
Other Adjustments that may need to be made, depending on which version you are upgrading from and to. These are broken down by which version they were added in. So if you are not currently at that version, you may need to make changes
Load the store front and again press CTRL+F5 3x times to refresh your browser cache. That will prevent oddly shifted elements due to stylesheet. (If you skip step 9, you will get the error message.)
Many bugs may have already been reported and fixes will be offered in the first post of this thread. You should always visit this thread immediately after a fresh upgrade to see if there are any immediate bug fixes If nobody has reported your bug, then please report it.
An online version of this file can be found here: http://www.opencart.com/index.php?route=documentation/documentation&path=98