mmm....
its very strange... normally if loading screen works on sp , must work on ivmp.
also i have win 10, i got the same problem but in twice games (sp and multiplayer)(infinite loading),
so my solution was to add a command line :
1 go to gta directory
2 add a file call commandline.txt
3write on it
idk whic support your gpu, but u can add all no problem-availablevidmem 3.0
-availablevidmem 4.0
-availablevidmem 5.0
-availablevidmem 6.0
-norestrictions
not necessary but i recommendif that dont solve your problems, search on youtube "infinite loading screen gta 4 "
ps sry for my english
