This error has recently appeared for our organization.
- The problem: We could not use basemaps and ArcGIS Online resources on ArcMap 10.8.2. Basemaps Disabled; ArcGIS Online Services Disabled; ArcGIS Portal Disabled.
- The error: "The underlying connection was closed: Could not establish trust relationship for the SSL/TLS secure channel."
- The solution: Chrome > Settings > System > Open your computer's proxy settings > Turn OFF use setup script. Every time the computer system is restarted.
- The why: an issue with zScaler.
On the Esri BeLux site, there was useful information. Third paragraph, Does this problematic network have a proxy server? The answer is YES. We are all telecommuting/hybrid so employees are using a third party vendor like zScaler which is adding a proxy server to telecommute.
I spent countless hours researching on my own, exhausting hours meeting with Esri support, and gritting my teeth with IT support. Esri insisted that it was an IT issue: IT blamed it on Esri's newest patch. I was provided with some great documentation: Esri Technical Support . Esri Perform a soft ArcGIS Desktop reset.
At the end, IT provided the solution.
