A few points to be made clear here:

• Workspace setting of "Enforce AWS Instance Metadata Service V2 for all clusters" has always been disabled
• Again, like I described in my original post, no changes made to AWS or Databricks, Serverless SQL Warehoues just suddenly stopped working with the error
• THe spark key "spark.databricks.hive.metastore.glueCatalog.isolation.enabled" is not even recognised in "SQL Admin Console" as per the attached screenshot