This happens when the NetSuite concurrency limit (set by NetSuite) for your account is exceeded. In other words, if you have a concurrency limit of 5 and you try to sync 6 flows at the same time, you may get this error. This is why a Flow scheduling session with experts is key.
- NetSuite SuiteAnswers Answer Id: 65791 gives guidance on determining RESTlet Concurrency Governance. You may also want to contact NetSuite and have them determine the amount of concurrency you need. You can then purchase extra concurrency licenses to eliminate this issue.
- Better manage the flow schedules so that not so many flows are syncing at the same time.
- If this error occurs, you can try again later (when not so many flows are syncing concurrently).
- Visit https://XXXXXXXX.app.netsuite.com/app/webservices/governance/governance.nl?whence=
And if you are SUPER interested, checkout this NetSuite guide.