Hi,
Thanks for the feedback! Glad to hear v1.5.3 fixed the main issue with rates not showing.
Version 1.5.4 Release:
I've just released version 1.5.4 which fixes an issue reported earlier where the shipping service names (Priority Mail, Ground Advantage, etc.) were not displaying on fresh installs - only the raw translation keys were shown. This was due to the language file being loaded too late during plugin initialization.
It also fixes the issue with the USPS text being doubled in some cases.
Regarding First-Class Mail not showing rate indicators: This is by design and there's no need to change it. First-Class Mail uses a simpler pricing structure - there's just one rate based on weight and whether it's a Letter or Flat.
Unlike Priority Mail which has multiple packaging options (Flat Rate Envelope, Small Box, Single Piece, etc.) that customers can choose from at different prices, First-Class letters don't have such variations. That's why USPS doesn't provide rate indicator codes for them in their Letter API response.
So "First-Class Mail $1.03" is the complete and accurate rate - there's no missing information. Adding "[SP] Single Piece" would actually be misleading since USPS doesn't return or even support that distinction for First-Class letters.
Please update to version 1.5.4 and let me know how your testing goes!