Ok, it seems that was a bug in v2.5.0 (and also v2.5.1 since it is just the one small hotfix) which was fixed in v2.7.0. The ultimate solution is to upgrade, preferably to the latest version of Cesium for Unreal, which will also require upgrading your UE version.
If that’s too difficult in the short term, I suggest you go back to v2.4.0. Now that Google has reverted the change on their side, there should no longer be a crash. However, you may need to delete the request cache if some bad data was previously cached. Details of how to do that may be found here: