Black Tank Backflush plugged at tank connection

Factory flush spray nozzles can be glued to tank OR they can be spun at high speed which melts plastic and 'welds' them to tank

When holes in spray nozzle get clogged (usually from hard water minerals drying out inside nozzle) they are virtually useless.
Now that you have hose cut off you could try filling hose with CLR and let it sit/soak




If it is an aftermarket kit then spray nozzle will be installed using screws/sealant
If you can't get to it to remove.....abandon in place and install new