Softver update not work
Displaying error panel (translated into Hungarian) what is nearly something like this: There is an error, no update is avaliable; Do you have live internet connection? Vivaldi 1.0.344.37 (Beta 2) (32 bites) -- installed USB mode, Windows XP SP3, Hungarian. Sorry for my English...
Please try agoin, may be the server has problems.
Or download Last Snapshot from https://vivaldi.com/download/download.php?f=Vivaldi.1.0.380.2.exe
Vivaldi 1.0.344.37 is the latest Beta-channel version of Vivaldi, and there are currently no further Beta updates available. As @Gwen-Dragon notes, a more-recent Snapshot-channel version is available as a direct download. Vivaldi versions "update" within their own channel only, since some users wish to update and remain within the more-stable Beta version channel.
That being said, an error message is not the normal response in a no-further-update situation. Normally, that message should read something like: "You're up to date! Vivaldi 1.0.xxx.x is currently the newest version available."