Thank you for submitting a ticket with us.
This issue is related to QuickBooks API, not Skyvia. Please take a look at this article
It states that applications cannot make more than concurrent 10 API requests.
When using Replication package all tasks are performed at the same time. With the "Incremental Updates" option selected 3 API requests are sent for each table - getting deleted record, getting updated records and getting inserted records.
There were 9 objects in the package and "Incremental Updates" option selected that resulted in more than 10 API requests. Also, this error can be caused by other packages that use QuickBooks connector from your Skyvia account or API requests from some other application sent at the same time to your QuickBooks account.
We recommend you to split your Replication package into several ones and look at the result.
Should you have any questions, do not hesitate to contact us back.