Is this a clean OJS installation or have you modified any files?
Did you install on Windows and move to Linux?
As it says in the previous link I sent you, change permission for Cache, Public, File folders and subfolders to 777 for testing.
Delete the files in Cache folder and subfolders (it should only contain 4 empty folders).
Yes, I installed on windows and moved to linux… …the only files I modified are template files. I actually created a separate template directory, and copied / modified the files there. no modification on core files like plugins. I’ve also deleted all cache and changed file folders permissions.
Is there any path I need to modify in the database?
PS: I also have an older install on the same sever, which has 755 file permissions on those folders, but I don’t experience that error there. old install has OJS ver 2.4.2. The current one in the new folder has ver 2.4.6.
Well, this is a bad idea!
I don`t know if there is anything wrong in your db or whether you can fix it by changing some values. OJS developers should answer you.
I suggest you install a fresh OJS (with your modified files) to a new DB on your linux server and check if the problem persists.
If it was ok, try exporting your content and issues to the new db.
Several classes are re-used across the CrossRef and Datacite plugins via symbolic links. Since symbolic links are treated differently in Windows and Linux, it is easy for them to be broken when transitioning from one system to the other.
A best case fix would be to untar a clean install of the OJS files on your Linux box, then copy over your local modifications again.
Thanks @ctgraham and @alirezaaa for coming to my rescue. I created a new database and moved all my templates, like you advised, and it worked! no more plugin errors.