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My name is Billy.
Quite often the filters for an attic unit are behind a ceiling or wall grill. Usually is about 20"x20" with a hinged side allowing to be opened.
Being a remodel, and if filter has not been changed you are likely running on "limit" and then shutting down...cooling and starting over.
Can you check the ceilings or walls and/or post pics of the installation?
If you have air conditioning or a 90% furnace..yes this can cause overheat. The ac coil becomes a catch spot for all the dust, debris, drywall dust etc.
Generally I would see at minimum a filter in the large ceiling grill