Thermoquad low-speed fuel well not filling?

These are easy carbs to work on. As I said in earlier post, I have had the acc pump plungers [ fairly new ones like yours ] double over; they then do not seal & you get no pump shot.
Unlikely to be a blocked idle jet [ IFR ] if you run a filter. The IFR will be about 0.031" or a little larger, so would need a large piece of debris to block...& get past the needle & seat.
Take the carb apart, easy to do!!! Unlike brand H [ & clones ] you not need any gaskets if you are careful. Especially if the carb was recently rebuilt.

Take pics &/or drawings of linkages/rods so that they can be correctly re-assembled.

Remove end covers over metering rods, then remove met rod hangar, rods & spring.

Remove all the airhorn screws, including the two under the choke blade.
Top [ airhorn {AH} ] can now be removed. Hanging down about 1.5" from the AH you will see the aluminium primary booster legs, one each side of the AH. Up end the AH & look inside the legs & you will see a small brass tube with a pinched end. That is the IFR & you can poke a piece of wire in it to make sure it is not clogged. Blow out with air if you have it.
Those booster legs sit on a small o ring in the black body.
These should be replaced. They are supposedly some sort of special design o ring [ x in cross section ]. I have always used standard 3/8" OD fuel resistant o rings, 1/16" wall thickness & NEVER had a problem. Readily available, no special kit reqd.

Acc pump. Remove the linkage screw on top of the AH & remove the S link. Tap lightly on the shaft & pump will come out the bottom along with the retaining valve.
If this valve is brass, shake it & you should hear/feel/see the small ball moving inside.
If it is pressed metal, you should see a small red pellet inside; this should move if you poke it gently with a paper clip.
Check the plunger. It has to seal in the bore. If it has shrunk/damaged, you get no pump shot.