I don't know if it's a specific issue or not, but in this french thread the user says that although he is regularly promoted from league 2 to championship, his reputation and sponsorship revenues are not increasing, or only marginally.
Are you aware of such a problem ?
Here is the name of my backup: Sponsor.fm
Regarding my problem, my reputation took time but it ended up going up, so that's good.
But as sponsors, I basically went from 50K to 170K in 8 years while I went from the 6th League to the 2nd League in 5 years.
My sponsor ranking in leagues
2nd league 24/24
3rd league 24/25
4th league 19/25
5th league 9/25
6th league 2/49