does some troubleshooting help here?
If not you may need to start a service request:
I would reach back out to the Samsung team here in that case:
In the US? --> https://www.samsung.com/us/support/contact/
Outside the US? --> http://www.samsung.com/visitcountry
Apparently there are lots of issues from the last update. Me and numerous others with s9 and s9 plus like mine are stuck in 3g after the update. Apparently Samsung smooged the pooch but isn't copping to it. I'm not sure what to do because nothing is working.
I've been having the same problem for a couple of weeks. I've tried all suggestions including factory reset. Concerned it maybe a hardware issue.. if it is wondering what the issue is and how I can fix it DYI