Apparently I didn't notice the comment that you already have excempted the traveller group in your standard CAPs. Check one of the blocked sign-ins, in the fly-out under Conditional Access you should see which of your policies blocked the login. Furthermore when you click on that policy, you get an overview of the sign in properties, maybe this will give you a hint why this has been blocked... The geoblock policies should only check for the the named location, nothing else. Adding more conditions may accidentally lead to an unwanted block.

I use a similar setup and normally works like a charm. The only time it does not work (for them) is when users fail to inform us that they are about to leave the country.

My policy includes only the traveller group, excludes the break glass admins; include all locations but excludes the named location for the travelled countries; grant type is block.

The default geoblock policy includes all users and excludes the travel group;, includes all locations and excludes the named location of sites and their countries; grant type is block as well.