There must be some conflict with some of your currently active plugins.
If you want to discover what exact plugin causes the error, you can temporarily disable all the active plugins, then if the problem is fixed, activate the plugins one by one until the problem reoccurs, so on that way, you will find the problematic plugin(s), then replace it with some similar or let us know what exact plugin causes the error, so we can try to fix the incompatibility.
Have you registered your theme?
without the registration, the update function doesn’t work.
This reply was modified 3 years, 2 months ago by Zex.