@JulieSillam - I have a couple of UMOs and the answer kind of ‘depends’.
Some filaments do just clog - I have some older colorfab filaments that I just use to print prototypes and they print brill for the first 20 layers and then just gradually clogg - so after a long print I swap out the nozzle and clean it (Let me know if you need to know how to do this.)
Some filaments respond badly to too long a pre-heat - thy clogg the cool zone and will not push through a ‘plugg’. To check this you could pre- heat to 210 and unload the filament and have a look at the end shape - if it looks like the nozzle inside then you are good to snip off and re-start as it is not the filament blocking.
Woodfill and copperfill just clogg because they burn.
Sometimes xt is being used by mistake - and this needs a higher temp
Your drive might not be clean - they can get filled with powder - open up the extruder and look at the hobbed bolt, give it apuff of air with a keyboard cleaner and/or brush it with a small brush. - to test it you could put the filament in, untension the syetem - just tension it until it grips the filament so you can’t pull it out backwards.
Check your delring bearing wheel in the feeder is turning round and not in a groove - I have replaced mine with a metal bearing (£2) on ebay)
Check the filament is smaller than 3mm (2.85) and moving through the bowden ok
So in conclusion it could be at the hot end which is blocked in the tip, or the cool zone or the bowden, or in the feeder not driving it from the back end, or bad filament
That is my brief cheat sheet for a UMO
nozzles do block - I have done a youtube video on getting them off if you need it.