One minor thought, depends on how old the fan is. If it's pretty ol
it will not necessarily have a solenoid to operate the louvres. In th big old ones from 20 plus years ago - much better quality and not s much to go wrong - the louvres are actuated by switching on, where th switch operating mechanism has a flat piece of metal on top and whe the cord is pulled, the flat comes down and lets the spring loadin open the louvres. These do need cleansing, as in previous answers, bu it may just be that the cover has been put back wrongly and it may b fouling the operating mechanism. If the kouvres break you might be i some trouble so treat them gently. They don't sell replacements for th old ones any more BUT; you can 'splint' the break with some slim spill of wood and two-part silicone or resin glue.
I've been there, done that and still have a fully operational (an clean) fan
docus
-- docusk