Off screen explanations aside, the amount of time between SW and ESB is a little hazy. The Rebellion has probably been on the run most of that time. (They haven’t been on Hoth long enough to know about Wampas for example.) Whatever missions Has has done for them, hasn’t taken him close enough to Tatooine to drop off the cash.
As I said before, I’m perfectly willing to buy that, it makes sense if the time Frame hasn’t been that long, that paying off Jabba has never been an option for Han yet prior to Hoth, or even that the time just got away from him. These however are only justifications for him not paying off Jabba, and not for him being a committed rebel in ESB in spite of the contradiction in that and how Leia (in particular) reacts to him (among others).
I’ve still yet to see even a probable explanation that resolves this with Han being committed to the Alliance in Empire, and thus justifiably taking the onus for completing his arc off of ROTJ.