DE system won't pressurize

I just cleaned my DE filter and after reassembling, I can't get it to pressurize. Its an old (20+ yrs) Swimquipt with the panel type filters. It seems to fill, but it never builds up pressure. Yesterday the needle would move up for a few seconds, then drop back to zero, today it just stays on zero. I've cleaned out the skimmer basket and the pump basket. I took it apart again and cleaned the rubber seal where the two halves of the filter housing go together. Is it possible that the filter is just shot? If it's worn would that keep the system from pressurizing or is there something else I could try. Any help would be most appreciated.

Thanks,
Barry

Have you re-double-checked all of your valves to/from the pool? I once (briefly) forgot to open my valves
after dis-assembling/re-assembling my DE filter to clean it...the odd noise from the pump told me pretty
quickly that I missed something. :) You might also unscrew the pressure gauge and see if water shoots
out when the pump runs...I assume you do that to purge the filter of air?

Thanks for the reply, ezpool. I found out it just wasn't priming. I had a pool guy come and look at it and all it took was to open up the skimmer by the pump and shoot water from the hose for a few minutes to fill up the line, then it primed up and pressurized normally. I'm glad it wasn't anything serious!