While I'm checking on this, as outlined in the Azure doc , have you tried both Azure Portal and REST apporach to enable /scale-up? Enable semantic ranking.
I understand you switched from Basic to Standard tier, Semantic Search is not working.
Yes, as mentioned in the doc: Semantic search - Azure Cognitive Search | Microsoft Learn Semantic search works for Basic and above Tier. If you haven't done , you may switch back to Basic and then to Standard again.