I went through the recommendations above, and then also called Quicbooks POS support. They said due to the new way POS and Webgility are connected, you can no longer reverse receipts inside POS that have been fed into POS from Webgility. You can only now refund.
We used the reversal for orders that would be custom or backorder, to then create a Sales Order with a deposit...which was also used to create the Purchase Orders, as needed.
So we can still get to the same endpoint by doing a Refund and then creating the SO with a deposit. It just takes a bit more time to refund when you have several items on the receipt, and also making sure we keep the payment method the same...compared to the Reverse feature.
Quickbooks POS support said to contact Webgility about being able to reverse...as it was being controlled by them. We called Webgility, and they confirmed that due to how POS and Webgility are connected, you can't reverse receipts in POS that are fed into POS from Webgility. But...you can do a reverse if you unsync the receipt from Webgilitty. The only issue with that is that it then puts the order details and "money" back in Webgility...and we want that in POS...because we would then end up with 2 receipts...the one we sell out from a Sales Order and then the one Webgility would create again once we shipped the order.
