I can't scan udp ports

Hello and welcome to this community forums.

You can find basic information on choosing the correct port list for your task here:

GSM Manual: 17.2.1 Selecting a Port List for a Task

Choosing to scan All UDP is usually not a good idea when not understanding how the UDP protocol is working as scanning all UDP ports on a single target might take multiple hours or even longer.

See also:

In some situations with port throttling, scanning all TCP and UDP ports can take up to 24 hours or more for a single system.

from GSM Manual: Scan Duration

Relevant existing community forum threads / postings: