Stratum protocol - problem with mining.submit method
The error is pretty self explanatory: you submitted a share that does not meet the requested difficulty. The pool requires that shares you submit meet a particular difficulty. If your shares do not meet that, then the pool will reject them. The shares that your software is sending to the pool do not meet the pool difficulty.

To fix this, either you are creating the submission incorrectly, or your miners are not mining at the correct difficulty.