My central vac has never clogged up in 15 years so I can't answer but you may want to check out https://www.centralvacuumstores.com/ They can probably tell you what to do.

I had to snake mine after cleaning up sheetrock. I couldn't get to where it was clogged though.

Is it clogged at just 1 valve or is the clog in a branch line which serves an entire section of the house? I grew up with CV and have had installed in my last 3 houses. I owned a hair salon and it clogged all of the time due to the fact that the hair dressers would pick up anything on the floor. Bobbie pins, clippies, wet hair, and God knows what! This always worked 4 me. If U have a shop vac, shut the breaker off in your box so it won't turn on when U insert your hose. Take the shop vac and insert the hose into the shop vac hose. Take a white plastic garbage bag and stuff it around the gap in the shop vac hose so U have no air leaks and the suction is not leaking out. That should bring the clog down to the elbow at the inlet. U can grab it out with your fingers or a wire coat hanger. If that does not do it U my need a little more help. The main feed tube at the tank is not glued and U should B able to pull it off the tank. If U have a leaf blower and a second person, this is what I have done. Take the leaf blower and fit it around the feed tube as best U can. Take a wet hand towel to seal it to the tube. Start the blower and then turn on the shop vac and that should do it. The clog will fly out the other way it went in. Warning, tape all of the valves closed which work as when the blower is turned on the valve doors will fly open and dust will B in every room. This should work 4 U. The last time I had a problem with a outlet it was $175, 2 come out and what they fixed was not the problem. I have a new person now who has been in the business 4, 40, years and is, now retired. He will work on mine. In the event the clog should make it into your hose just use the shop vac on the inlet, hose end, sealing it with the plastic bag and bang it on the floor while the shop wac is on. It has always worked 4 me. Let us know how U make out. This is a forum to learn.

Good Luck!