Summary
Multiple Microsoft SQL Server database connections in Retool have suddenly become inconsistent/intermittent as of today, despite working reliably for months, with no changes reported on the database side (confirmed by IT) or the Retool side.
AI Response
A very recent Retool change is the most likely culprit for MSSQL resources that break suddenly with no database-side changes: as of July 27, 2026, self-hosted deployments now reject Microsoft SQL Server resources using Windows Authentication with custom ODBC connection parameters that are not on Retool's approved allowlist (previously these were only logged as warnings). If this applies, search the dbconnector/backend logs for 'MSSQL Windows Auth ODBC connection string parameter not on allowlist', then remove or replace the flagged keys (for example, use the resource SSL/TLS settings instead of Encrypt/TrustServerCertificate, and ConnectRetryCount/ConnectRetryInterval instead of LoginRetryCount/LoginRetryInterval). If the behavior is truly intermittent rather than a hard failure, it more closely matches known Azure/MSSQL idle-connection drop-outs, which have a documented solved workaround.
Sources
Microsoft SQL Server (Windows Authentication): unsupported ODBC connection params are now rejected
Announces the July 27, 2026 change that now blocks self-hosted MSSQL Windows Auth resources with unsupported ODBC connection params, including how to detect affected resources and remediation steps.
A solved thread on intermittent Retool-to-Azure/MS SQL connection failures that corroborates the inconsistent-connection symptom and shares an accepted fix.
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