How to bias a tube amp with a Multimeter

I would try 2 things..
First confirm correct operation of multi meter using an electrical outlet or a battery of some type..
Second,go ahead & set up the amp,connect to a source & send a signal,confirming operation of amplifier(just be cautious & slow with the volume control)..If the MM is working as it should & you get sound from the amp.then you’ve got something going on with either the biasing test block or worse...

Is it possible the bias pots are adjusted so low there is no flow through them?Maybe try turning the pots up(make sure no signal to amp & volume control turned down) & check again...Other than that,my next move would be opening the amp up & checking the connections at the bias test terminals...

Paying to have the amp biased won't help you in the future..For that much $ I would want at least a diagnostic of the test point problem included..
 In the mean time,I would run the amp & see how it sounds..If it was properly biased before going into storage,there's no reason to think it's drifted off much..
I might also consider buying another meter,I mean $20.00 for another meter that can be returned is a lot faster & cheaper than the alternative..Good luck..

^^^ Thinking about what he's saying..Try backing one of the + screws out & see if it comes all the way out or has a stop point..If it has a stop point move the ground screw out as well & retest,you never know...

Any luck?