Please watch this video to install an SD card. If after watching the video your SD card is not detected.
Please pay attention to the 1.34 minutes in the video. Do not select option 1 “Use for extra phone storage”.
SELECT OPTION 2 ” Use for Portable Storage”
If you selected the 1 Option. Please remove the SD card from the T8 PRO.
Then go to SETTINGS > STORAGE > Select the SD card and click Forget SD Card.
Now you can install the SD card again and select Option 2.