I assume you took the old foam out and that you had to clean the remains from foam rot?
If that is the case, you can check if some of the copper traces on the PSU PCB have been damaged by the foam rot. Sometimes you need a magnifying glas to see it, but then you might detect copper traces partly ‘eaten away’ by foam rot. If you have such a thing, you can solder a wire as a kind of by-pass.
Also check if there is still foam rot remains on connectors or components. And check if there are components that are damaged, like for instance capacitors that look puffy.