I have Tried to re install the game 3-4 times, also tested a different vanilla version of the TDU as well, the problems are the same but different.. its some cars and mission that not works on the platinum.. I also played a lots of TDU2 unofficial path without any issues.
I guess its maybe some problems with the platinum its self ?
I Had EXACTLY the same problem/sulution in this reddit thred when I installed the game, I was close to give up the platinum entirely.
I installed tha same waw Nick-synth did
https://www.google.com/url?sa=t&source=web&rct=j&opi=89978449&url=https://www.reddit.com/r/tdu/comments/tkfef1/endless_loading_screen_with_platinum_mod/&ved=2ahUKEwiNi4Sq8b6FAxVmERAIHaxLBaMQFnoECA4QAQ&usg=AOvVaw26dL_E266YmM_BBFbxqEuI