Stamps.com is believed to have resolved the issue.
We are continuing to monitor the issue and will update this incident accordingly.
All systems and processes are returning to normal.
Posted Sep 27, 2019 - 16:06 CDT
Update
We are continuing to monitor the increased response times and related issues when purchasing labels, adding funds, and similar actions through USPS carriers.
Postage providers affected are currently Stamps.com and Endicia. You can find their respective status pages here: