Hi samdev87. Welcome to the Spotify Community!
Is this the step you are following? In case you can't see the option to save to SD card, please log out of the account, close the app, re-open and then sign in again.
If the issue persists, would you mind sharing what you're seeing?
Let's also make sure you have the latest Spotify app installed on your device.
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As suggested above, you may be able to solve this by Signing Out of the Spotify App on your phone, or uninstalling it and reinstalling it completely.
Since this is a new SD card, cand you confirm whether or not it shows up under Settings > Device > Storage on your Android phone?
You may need to format the microSD card from that menu as well.