Andy, this is something we need to be sorted out. I use Microsoft edge and I've never been able to select a base to create new units.
My work around has been to use the map controls to hide everything but the bases so they could be clicked on directly.
When war is declared the map controls are disabled and since the bases are covered with supply units and defensive weapons that can't be moved I either have the choice of disbanding everything just to make a few offensive units (then until I move them the defensive units can't be made). Not a process that would survive in a PVP situation.
I've mentioned it before and never got a response. I'm not the only one having this issue. Even people with firefox and Chrome have it happen from time to time requiring a restart (which doesn't work for me)
And no, clearing the cache has no effect the link to select a base from the list is simply dead on the pop-up. This is a very big issue for those that suffer from it.