Welcome to the community, we are so happy to have you here with us.
I did some research and it looks like this specific error you are receiving is something that might be related to an issue we are aware of and currently have escalated to our senior support/product teams. My recommendation for you and anyone else who is seeing this error is to reach out to support so they can make sure that this is related and if that is the case make sure you are notified as soon as this is resolved.
-Erin: Your Friendly ShipStation Community Manager
Received data containing a ready time later than the latest allowable ready time for the location (Bad Request, Carrier Error Code: 9510113). (400, 1015957d-36dc-4db2-86f2-0f42218fd7fd)
This is the code I get, no matter what time or day I try to schedule the pickup.
I'm getting this same error code - not surprised you haven't gotten a reply from shipstation about this. They like to ignore actual issues (like the email issue that's about to be a REALLY big problem in about 9 days)