I would strongly suspect it really is too many observations. If you look at how many observations Manatee and Hillsborough Counties have on iNat, it’s about 250,000.
On GBIF (which is only getting the subset that are RG and appropriately licensed), Manatee and Hillsborough Counties have about 110,000 obs.
So around here, it looks like iNat has around 2.5 times as many obs as GBIF. Uploading your shape to GBIF shows ~116,000 observations, thus it seems likely your shape encompasses more than 200,000 observations on iNat, exceeding the limit.
