is it just my script or submit button is disabled after uploading in this version v4.0 rc1
Your server is not allowing the script to insert video in database. This could be because of multiple reasons:
Check your server for all the required modules and configurations. Your server must have all the required modules to run ClipBucket: https://clipbucket.com/cb-install-requirements/
it cannot be my server. i created a subdomain. installed version 2.8.1 and submit button works well there. it is definitely from the v4.0 script
I believe the issue is with your PHP or MySQL version as the latest version supports different version of the modules. V 2.8.1 is very old and has very different requirements.