Now I removed all 5 WA extensions from Extension Manager, opened Dreamweaver, closed DW, deleted winFileCache ***.dat file, reinstalled all 5 WA extensions in Ext Manager.
Opened Dreamweaver, WA installer completed 3 stages for Data Bridge.
Then it started step 1 of another install, but this was also titled 'Installing Data Bridge'.
After a minute or so, it came up with the same "ERROR: Could not connect to WebAssist server ..."
Closed this then tested Data Bridge with one of the SBs. WA Activation box appears.
So new version 1.2.0 is installed properly.