Hi La-Qa,
First try a different browser and from different system. Try to cold restart the wasp probe and clear browser cache memory before retrying and check the status and that you don't have any failure in any other probe that the USM needs to load properly (wasp, nas, trellis, discovery_server). Check if the the connection between UIM and the the backend DB is working as expected. If it never loads after a restart try to catch if there's any error or warning in the following logs:
/probe/service/wasp/portal.log
/probe/service/wasp/wasp.log
/probe/service/trellis/trellis.log
probe/service/nas/nas.log
If you see any error there, try to search by keywords in our UIM KB:
CA Unified Infrastructure Management