1
If pressing the Num Lock key or Fn + the Num Lock key did not resolve the problem, the Mouse Keys setting may be enabled.
Open the Settings App.
Go to Accessibility - Mouse.
If the Mouse keys setting is enabled, disable that setting.
2
If that also does not resolve the problem:
Open Command Prompt, then paste in this command and press Enter:
msdt.exe -id KeyboardDiagnostic
Run that Keyboard Troubleshooter to see if that can solve the problem.