I have set up two shipping methods.
But USPS is not showing up on the checkout page.
Any idea? I use magento version 22.214.171.124.
As the issue you have posted is not having more information. I have given you the basic solution to fix it. Once you find the exact issue post it back. There are 2 major possibilities for your issue.
Invalid account information : To find and fix this issue, enable the debug mode in the extension and try once again. Now check the debug log, error log and exception log. You can find information in it.
Incorrect configuration of the extension : You might have made your maximum package weight less than the product weight, wrong credentials, credentials may be for live account but chosen development in mode. Might have not enabled for checkout.
Note: USPS require the from address to be US. Please check your store settings and confirm it is set to valid US address.