If you can get a prompt when you don't watch Tik Tok on WeChat, but you can't get it when you watch Tik Tok, then you definitely don't have the right to set a "floating window". Let me tell you how to modify the settings:

My mobile phone: my true self

The first step is to open the phone "Settings".

Step 2, find "Application Management" on the settings page.

Step 3, find the "application list" in the application management.

Step 4, find "WeChat" in the application list to enter.

Step 5, on the details page of WeChat, open "Allow the display of floating windows" (blue means open).