As mentioned by gokongming, please check and update the Samsung Pay app to the latest version.
Also, try to clear the cache and force stop the app.
Follow the below steps to clear the cache of the Samsung Pay App:
Open Settings >> Apps >> Samsung Pay >> Storage >> Clear cache.
To force stop the app: Open Settings >> Apps >> Samsung Pay >> Storage >> Force Stop.
Then try to reboot the device and check. Sometimes a simple reboot will fix the issues.