If your address bar suggestions suddenly stop working, check this thread out
I decided to give the vivaldi snapshot build a try, however later on I decided to switch back to the stable release channel. In the process, the address bar suggestions completely locked up - regardless of how I messed with the suggestion settings, nothing popped up.
Apparently, in the vivaldi's profile folder (path's listed in vivaldi://about) there's a file that keeps address bar typed history, as well as vivaldi://settings preferences. It's located in the Local App Settings\smpognobbkildjkofajifpdfhcoklimli\ folder, as .log file with a number for a name (000006.log for example).
Deleting it causes vivaldi to create a new empty one on the next run - preferences will be gone but the address bar will suggest websites again. Alternatively, one can try to truncate it so only part of typed history and preferences is lost - but if vivaldi considers the .log file corrupt, it'll be moved to the 'lost' folder.
Apparently in the process of moving between snapshot and stable releases my .log file got somehow broken but not enough for vivaldi to consider it so - the settings were loading fine, but typed history was not. As such, address bar's suggestion feature in general stopped working.
Vivaldi has some brief info about Local App Settings folder on the help page but it doesn't mention it stores address bar typed history too. I wouldn't consider it a bug though, since using one profile for snapshot and stable releases is generally a bad idea and I brought my issue on myself. Still, I wanted to share since someone's bound to run into the same problem sooner or later.
Good to know.
By the way if you want you can run both stable and snapshot side by side. You only need to install one version as a "Standalone".
You can do so when you click in the install window on Advanced select the dropdown menu for Install Type than select Standalone. Now the only thing left is to select an install path (I recommend not to choose a path that interferes with your "normal" install - just to be sure nothing get's messed up).
So you can use the stability of the stable version for every-day-browsing and the snapshot to try out new functions and test stuff.