If the fan blade won't turn by hand, there is a physical obstruction. It could be inside or outside of the motor housing. You are going to have to find that physical obstruction. That may require disassembling the fan motor housing to look. However, I would start by a thorough search from above and below to see if anything is blocking the fan from turning.
And remember, if someone thinks YOU are an idiot, it may just mean that THEY are an idiot and can't see logic. Also, the basic questions MUST be asked, even if they sound extremely simplistic, so WE know what avenues need to be pursued. In another thread, someone posted because he didn't have 12v power to his RV unless it was plugged into a power post. After a couple of pages of diagnostics, someone finally asked if his disconnect switch was turned on. The most simplistic question fixed the problem. His disconnect switch had gotten activated accidentally.
