Yongnuo 622c and 430 ex ii

Hi everyone I just purchased the yongnuo 622c flash trigger. I purchased it to enhance my skill with off camera flash photography. I received the unit and i used it with my canon 430 exii speedlite. I was able to use the high speed sync function on the speedlite in conjunction with the flash trigger for maybe a week. Now every time i try to use high speed sync on the speedlite off camera, it wont sync past 250 without seeing the black sync bar within my picture. Is there anything I should do differently to troubleshoot the issue?