This sounds similar to a problem experienced here at Southwark with SSA 2018.2. The onsite engineer had to make a few changes to get that resolved on the day of installation.
To be honest it was the least of the problems with SSA 2018.2. The overall way in which much of the administration has been moved into the UI away from the admin console caused so many problems. Personally I found it utterly unworkable and impractical – see my earlier posts on the Knowledge Hub. Moreover, the actual SSA service itself just kept on failing (layers not showing etc.). After five painful days we had to revert to v12.2.1.
Corporate GIS Manager
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160 Tooley Street
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Southwark Maps - public facing mapping service