I updated IDEA to 2018.3 now I can't use Kotlin because I get Incompatible with the current IntelliJ IDEA version Please what can I do to resolve?

Update the kotlin plugin. There is a specific version for 2018.3

Thanks, but I tried, didn't seem to find any updates

Try to delete plugin and install it again manually

And reboot the IDE like in any plugin update.

Yeah, thanks after a few restarts I was just prompted to that an update is available. Updated

It seems to be a common problem for IDEA plugins. Please also vote for https://youtrack.jetbrains.com/issue/IDEA-202648