my airdrop on the Mac keep saying incoming block connection

What year model Mac and what macOS version is it running?

see > Identify your iMac model - Apple Support

Check your Firewall Preferences or Settings in macOS Ventura.

see > Use AirDrop on your Mac - Apple Support

Make sure that incoming connections aren't blocked in firewall settings:

• macOS Ventura or later: Choose Apple menu  > System Settings. Click Network in the sidebar, then click Firewall on the right. Click the Options button, then make sure that “Block all incoming connections” is turned off.
• Earlier versions of macOS: Choose Apple menu  > System Preferences, then click Security & Privacy. Click the Firewall tab, then click the lock  and enter your administrator password when prompted. Click Firewall Options, then make sure that “Block all incoming connections” is deselected.