my universal clipboard is not working

Try turning your handoff settings off, then on:

• Mac: Choose Apple menu  > System Preferences, then click General. Select “Allow Handoff between this Mac and your iCloud devices.”
• iPhone, iPad, or iPod touch: Go to Settings > General > AirPlay & Handoff, then turn on Handoff.

Use Handoff to continue tasks on your other devices - Apple Support

Make sure you are signed in with the same Apple ID on all of your devices and that all of your devices are on the latest OS update.