Super Mario Maker 2 only lets you upload 32 levels
Super Mario Maker 2 appears to have a hard limit in the number of courses players can upload. Once you’ve shared 32 levels online, that’s it. It seems there is no way to increase that at this time.
In the original Super Mario Maker, 100 was the maximum. Players started at 10 and the amount increased 10 for each medal earned.