I agree that the error is coming from our MySQL server. After reading the article Debbie offered and spending a somewhat long and frustrating day learning more about MySQL server configurations than someone like me should ever know, I am still unable to connect to our MySQL server using both the base release of TDA 3.5 and a trial of the Pro version of TDA 3.5.
At this point, I have to turn the conversation back to TDA developers. TDA version 126.96.36.1999 will connect to any of our MySQL databases using passwords input via CPanel > MySQL Databases > Database Users.
Why would 3.4 work properly and 3.5 fail? There has to something that changed from 3.4 to 3.5.
I am also able to connect to our databases using MySQL Workbench, but only if I set the “Use the old authentication protocol” to yes. Perhaps it would be possible to add a similar setting to the connectoid properties in TDA.
I am loathe to make global changes to the MySQL server startup string since there are a number of websites we run that are working just fine now.