This is really an answer rather than a question to a whole bunch of other questions. My Bissell model 25A3 previously discussed had the same symptoms as described. Although the long winded answer for me was not correct, it assumed there was a clog in the line, but this answer did set me on the path to solving my problem. There was not a clog in the line, rather a new water pump was needed. Removing the lid to the tank as suggested did start the spraying from all sprayers, top and bottom. But why? The answer is my old pump even though responding to the tank lid being taken off was not strong enough to overcome the reduced vacuum created when the lid was on. Vacuum is the way the water pump primed but will not prime with less vacuum when the lid was on. It simply could not overcome the reduced vacuum when the lid was on. That's it! A new pump was all that was needed.

Ted Lessler, July 2022