Should I switch to other class when my MSQ progress prevents me from level up?

[Iscah]

I have access to RDM so I should have access to 50-60 but the quest I completed for him gave me no EXP despite what the quest read.

Yeah, I thought of it last night that if you can sign up for red mage then you must have successfully registered at least Stormblood to your account. (If you have access to Hrothgar and Viera in the character creator, then you have everything registered.)

Hopefully the easy fix works for you, otherwise post to the In-Game Bugs subforum and see if they can help you there.