I’m not sure if I missed sth in the manual or tutorial vids, but I had to experiment around a bit to figure out that on my config (Pro Tools Ultimate 2023.6 with MB 1.5.19) I had to remove the shortcut key assigned to Create a Marker (NumPad + Enter) from Pro Tools.
Before that MB just started to make Location Markers and writing in eg: //01:59:58:02 - which is the timecode. It then returned a Range Error and kept making markers on the TC Selection I had in Protools.
Hope this helps - since after removing the Numpad+Enter shortcut everything works like a charm.