Why can't add I Motion Graphics Templates to Premiere Pro 2020 Timeline
I don't work with MOGRT too much but I assume this is similar to working with AEP comps that you live-edit within Premiere.
Try either dropping into the project first, then into timeline.
Try rolling back to last 'main' version of both AE and PP - so still using 2020 but e.g from 14.5 to 14.0 - often issues appear with PP/AE mismatch during small updates and dynamiclink can be unpredictable.
Hope this helps