We have been using the old ship manager for 24.0 and received this pop-up last week on 5/23 when trying to ship. I updated again today, 5/28, and now the pop-up no longer appears. I'm curious if the deadline has been extended. We did try out the "new" shipping manager, and would have to say it was a very terrible experience.

Right away (for FedEx and USPS) I've noticed there were no options to create multiple boxes per shipment, no reference fields to use for the carrier label (we typically insert PO numbers and SKU numbers), no option for 3rd party billing, and our stamps.com balance did not reflect (when shown "connected" in the settings) when trying to use USPS as a carrier. We also had issues connecting our UPS account to the new shipping manager, which we did not have the opportunity to experience, but I would assume it would yield the same outcome as with FedEx and USPS. I hope they work this all out before cutting us off from the old shipping manager.