If you have a Lenovo computer, then it is very likely that the problem is with Lenovo branded software.

Follow these steps:
Open the Start Menu
Enter “lenovo”. Either Lenovo Vantage or Lenovo Settings should appear.
Open either Lenovo Vantage or Lenovo Settings

If it is Lenovo Vantage:
Go to “Hardware Settings”
Scroll down to “Camera privacy mode”
Turn off this mode

If it is Lenovo Settings:
Click “Camera”
Select “Normal” mode instead of “Private / Confidential” mode
If nothing appears when you enter “lenovo”, try entering “settings”.

The following option is also possible:
Vantage or Settings are not found, but there are Lenovo ThinkVantage Tools.
In this case, you need to run this program, select the “Web Conferences” menu item in it. The Communications Utility program opens, in it you need to click the “Show my video image” button and make sure that the gray screen is gone.