If your BURST Toothbrush is not vibrating the First step with the brush is to remove the brush head and thoroughly clean the brush handle, head, and especially the metal prong the head sits onto. You can use rubbing alcohol to clean the brush or soap and water mix. Then try the brush again and see if this has resolved the issue.
If you have a new or spare replacement head you can also try this on to see if the issue is with your replacement head.
If this reset has not resolved the issue then submit your warranty claim through the BURST website here: https://www.burstoralcare.com/register
Here is a video on how to clean your BURST Toothbrush: