Thanks for contacting TextNow Support, and sorry to hear about the SD card slot!
A quick test you can try on your end (assuming you haven't already) is to pop the SD card into another phone and device. If the card reads fine in another device, it's definitely an issue with the reader on your phone. If it doesn't read it, it might be a problem with the SD card itself.
To discuss replacement options, please give us a call at TextNow Support: 1-888-250-5255, Mon-Fri 9am-10pm, Sat-Sun 9am-5pm EST.
We look forward to hearing from you!