My MG995 servo is not working with lipo power cells even though they can provide the right current

Question

I am trying to run a sweeping code from an Arduino to an Mg995 servo when powered from the Arduino it works but when I try to power from 2 lipo cells rated at 8A 3.7v each the servo doesn't rotate even when I put it through a voltage converter the servo doesn't move at all but only when u try to measure the current with my multimeter I can see the servo start to vibrate a little though it is not the desired outcome its something. can't figure out what's wrong?

1. gets powered with Arduino but I need to power multiple which Arduino cant handle
2. i powered with lipo cells which dosent work
3. lipo cells + voltage converter dosent work
4. lipo cells + voltage converter + test current with multimeter makes it vibrate randomly