If your xArm Studio and firmware verison are earlier than 1.5.0, that may caused by the software issue. Update both the xArm Firmware and the xArm Studio to the latest version(≥1.6.1) will solve the problem.
Here is the guidance to update the xArm Firmware and the xArm Studio:
If the step 1 does not work, please refer to this article and contact email@example.com
What should I do if I have a problem with UFACTORY xArm? | UFACTORY Help Center