Toilet won't flush bought new one put hose in pipe while it was off, water drained installed new toilet and still won't flush bowl fills but won't go down

A hose is no match for 1.6-3 gallons of water all at once. Start with a toilet auger or take it off the flange and rod the drain. A blocked vent causes slow or inefficent flushes more than no flush.

bowl fills but won't go down

Does that mean that the water won't go down at all or;
The water goes down very slowly or;
The water goes down slowly?

Does this happen the first flush or can you flush once then the water won't go down or goes down slowly the second time?