You should upload a sound file. It's hard to judge music without listening to it.
You also didn't mention which style you are trying to write in, so that makes any technical feedback very hypothetical too.
But in general, canonic imitation normally involves counterpoint. From a distant look at the score, we can see several hints that your piece goes against the most general principles of good counterpoint: not much rythmic contrast, a lot of parallel motion; not much voices independance. Visually, it doesn't look like counterpoint which is puzzling for a canon. When the violoncello enters, it plays the same melody as the violin, on the same beats; this is not canonic imitation (you need to shift it by a time interval). Here you are simply doubling the voice, which is quite redundant, especially in a small ensemble.
For the rest, I didn't go into details, because it also depends on the style you want to emulate, but there appears to be some errors. Melodically, you have some problems (A2nds, the line doesn't imply clear harmonic motions, repeated notes, and I'm not sure about your use of leaps but I would need to hear how it sounds). As the other commentors have mentionned, your intervals are not properly treated as well (as said previously, parallel 5ths and 8ves, dissonances not resolved in the "right" way).
I think you need to study counterpoint before trying to write canons. Or start with 2 voices rather than 4. It seems you could benefit from a more gradual approach