I'm currently attending summer school but I haven't PAID my agreement yet (i confirmed the payment agreement though) because my osap didn't arrive yet due to some issues.

SOLAR is supposed to open for me tonight, will SOLAR not let me choose courses due to my remaining fees? Please help, this is urgent

It depends whether or not you're considered "balance outstanding" I think - I'm not sure when the deadline for payment is.

Either way though, there's nothing you can do about it between now and midnight. Even if you pay it, it won't go through in time.

Could you elaborate? My outstanding fees are from spring/summer tuition. I tried going on solar right now to see if i can add/remove a course for the summer session, and SOLAR didn't block me off. Does this mean i'll be fine for tomorrow (midnight)? :/ ... Really worried