[JRTJH]

Robear,

The plumbing lines for the black tank flush system is all PEX. If it wasn't kinked before, there's almost no chance that it would suddenly "kink and stop flowing". You didn't say whether the black tank was filling just that you didn't hear water flowing. If the tank is relatively full (over half full) you probably wouldn't hear the nozzle "spraying against the tank walls" since it would be underwater. You should hear the anti-siphon valve "buzzing" under the vanity, but often from outside, you can't hear or can barely hear that valve.

If it was working previously, then it should still be working. Dump the tank, let it drain completely, then turn on the flush system and watch the sewer hose to see if anything is flowing. You can, if you watch closely and don't walk away, close the black tank valve for a few minutes, then open it and see if you get a "gush of water" as you open the valve.

But, to answer your question, "Maybe the line is kinked". Probably not, since it's rigid PEX tubing and if it has been working in the past, on a 2013 trailer, there's almost no chance that the PEX suddenly kinked.