Previously, I can launch ArcMap or ArcCatalog and create a database connection to our SQL Server databases.
Today, when I try to create a database connection to SQL Server, it flags me saying
"Unable to connect to database server to retrieve database list; please verify your server name, user name, and password info and try again. Connection was attempted with an older version of SQL Server client communications software that is not supported."
However, when I try this on another computer with same version of ArcMap/ArcCatalog (version 10.5.0.6491, it works without problem. I'm connecting to the same server on our network.
What is going on? Appreciate any help.
You've probably checked this already, but when I used to get this error (back when we had an ArcObjects/C# custom add-in for ArcMap) updating the SQL Server Native client on the client machine would fix it. I seem to remember you could download it from my.esri.com, going to downloads and picking your software version; then it would include the appropriate client for your version in the downloadable files.
Can you see if the SQL Server Native Client is the same or not on both machines you have tested?
I don't have SQL Server on my development machines since I simply connect to the network server used for storing our databases.
So both ArcMap/ArcGIS on different dev machines actually just connects to the same SQL Server databases on the same server. Why one machine can connect and the other can't is totally confusing.
See below for a link to the ESRI docs about connecting ArcMap to a SQL Server EGDB.
Connect to Microsoft SQL Server from ArcGIS—ArcMap | Documentation
I think every machine running ArcMap has to have the appropriate SQL Server drivers installed. Back when this was happening to me installing the SQL Native Client installed the drivers I needed (that was 4 or 5 years ago), but maybe today its just an SQL driver you get from Microsoft... about half way down the page is the title:
I would try installing the recommended SQL Server drivers again on the problem machine... maybe something has gone wrong with the drivers installed there already.
The only other thing I can think of is that the user name and password might be wrong and the message you are getting is just generic for both errors (I.E. connection problems AND login problems)... but the UN and PW worked on the other computer so I doubt that's it.