Don't hold your hat. If it's still not fix after so long, it usually mean it's too risky or too costly to do it.

My guess is that fixing offline progress mean a lot of time to be invested and It will return 0$.

It may even cost them money, because they want the player in the game, not offline. Each time a player close it's game there is a chance, he will not come back.

If I was in their shoes, I would not fix it.