Keyboard issue on iPhone right side

(1) Try and Force Restart your iPhone EXACTLY as shown below and see whether that resolves the issue:

• Press and quickly release Volume UP button
• Press and quickly release Volume DOWN button
• Press and Hold the SIDE button until an Apple logo appears and then release the Side button (Can take up to 20 seconds. (DO NOT release Side Button when invited to Slide Power OFF). 

(2)  If that does not help, then contact 👉 Official Apple Support OR you can always get your iPhone examined at the Apple Store 👉 Genius Bar Reservation and Apple Support Options or at an Authorized Service Center for further diagnosis and evaluation.

Axel F.

If you have a protective case or screen-protective film, remove that and test again.

With no case and no film, and if this insensitivity also affects apps and whatever else on the right side, then the display or digitizer hardware is probably failing. Which means a repair or replacement.

Contact Apple Support: Official Apple Support