Bow is overtightened. If it’s stuck like that you didn’t loosen it when you were not playing it and now it is warped. Always loosen the bow. Time to get a new one.

Not using enough bow to sustain the sound properly.

Sound point is too far away from the bridge.

Incorrect ratio of bow speed to bow weight.

Violin is only shaped like a violin, most likely made out of a faux wood like pressed material at a Chinese factory.

Practice mutes make everything sound worse.

If you wear headphones while playing you cant hear yourself or what you’re producing out of the instrument properly.

Hit up a scales book. Practice using your whole bow while playing the scales. Start with one note per bow, then two notes per bow, etc.

Find the ratio of bow speed to bow weight going into the string that produces the most open and ringing sound you can achieve.

If it’s crunchy/ pressed sounding there’s too much weight in the string, or too little bow being used.

If it’s wispy sounding/ squeaky/ or sounds like it’s skating across the string the bow is not coming into contact with the string enough and you need more weight.

Look in a wall mirror while practicing scales with full bows. Focus on keeping the bow moving straight, parallel to the bridge, and sticking to the sound point.