Well… I am new to this 3D printer world… what a mess… so … I had the same problem recently. If it is ABS … get out the nozzle head and get a syringe with some acetone, and slowly insert little the acetone to the nozzle (all this, with the da vince off and cold and without puting acetone on the circuits) . With another metalic wire inserted in the filament guide and nozzle (from the bacl, not the point) just move up/down , out, cleaning it as the ABS dossolves
Then, let the acetone evaporate for some time, heat the nozzle (it will make some noises as the acetone evaporates)… and insert the new filament to push the remaining one.
It requires some time, but… it works