Paypal Sandbox：发生了内部服务错误

I am trying to make first call with Rest Api Sdk PHP as wrote hear. Receiving always INTERNAL_SERVICE_ERROR

debug_id for example: 16d1628fcae04

I just realized that I forgot:

$payment->setTransactions(...);

before calling

$payment->create($apiContext);

Without transaction endpoint returns INTERNAL_SERVICE_ERROR and not as expected VALIDATION_ERROR or MALFORMED_REQUEST

Fixing this solved the problem.