The German Federal Constitutional Court has now issued its long-awaited decision (source) in case 2 BvR 739/17 which was a complaint against the German Ratification Law under which Germany was to ratify the UPC.
The complaint succeeded on purely procedural ground in that the law was not passed by the required two-thirds majority of the members of the Bundestag (the vote in favour was unanimous, but insufficient members voted). However, the more substantive grounds of the complaint failed.
Therefore, it will be possible for Germany to ratify the UPC (or an amended version of it which doesn't involve the UK) so long as voting procedure is properly followed.
Timescale for any progress of the UPC is uncertain, in particular because it will need renegotiating after the UK announced it would no longer be taking part.