The port side forward fuselage main deck cargo doors on each of the HJG hosted B737-300 and -400 SCD type simulations "DO NOT" open/"ARE NOT" animated .... as stated within HJG's forum based B737 manual.
That is the way these models were compiled and then supplied to HJG.
See paragraph 1.05 .... "HJG B737-300/400/500 3D MODEL REPRESENTATION" within "SECTION 1" of the following-linked forum based HJG B737 manual ....
May I also suggest .... in future, and in regard to all HJG simulations, it's better to seek advice directly from the HJG forum .... since that's where the expertise which has either brought the HJG simulations into existence. or otherwise supports them, is located. This request is simply intended to ensure not only the best and most thorough, but also, the quickest resolutions for end users
I've only just seen/stumbled across this query here by pure chance/accident