Hello @Saleh,
There should be no issues for scheduler compatibility with older angular versions, for example you can find an example of integration with angular 11 in the following topic:
So likely the issue in your case is connected with project settings, but it’s hard to suppose what exactly goes wrong without more details, so it would be helpful if you send me a simplified demo with all necessary files and run instructions, that I will be run locally and check out what exactly goes wrong.
Kind regards,