You will have to start from zero
You had the saw working satisfactorily right? Then something happened and now the blade won't stay on. Retrace your steps. What did you do different?
I would assume the bandsaw needs a complete "tune up" meaning you have to back away all the blade guides so they don't even touch the blade. Place the blade on the tires and slowly rotate them to see what happens. The two lower wheels must be in the same "plane" that means a straight edge place across the rims must show no gaps.
If there are gaps on either side of one wheel, that wheel may be out of alignment OR it may be the opposite wheel. That's why I suggested grasping the wheels and checking for play, up or down OR side to side. Something changed from before to now.... what was it? The upper wheel sorta "floats" on it's stubby axle and is spring loaded for the tension. It should only move up and down, no side to side movement.
If the upper wheel moves right to left, then that must be corrected.
I am used to the upper wheels sliding in a track up and down, but the track is restricted from moving side to side. See what you can determine.
The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)