On a new computer yesterday I downloaded and installed SynkTrayzor (latest downloadable from the site) by taking it from the page Syncthing | Downloads
From the same page I downloaded and installed the latest available version of Syncthing, v1.26.0.
Curiously if I launch SyncTrayzor.exe, Syncthing doesn’t start and I get the pop-up:
Syncthing failed to start.Please read the log to determine the cause.If you see the message “FATAL: Database could not be opened”, close all other open instances of Syncthing. If SyncTrayzor crashed previously, there may still be active Syncthing zombie processes. Use the menu option “Syncthing → Kill all Syncthing processes” to stop them, then use “Syncthing → Start” to start Syncthing again.
But there are no active processes to close of Syncthing or connected to Syncthing (I checked). However, even if I “End all Syncthing processes”, I get the same pop-up again
HOWEVER (!) if I launch a portable version of Syncthing, v1.1.29 Syncthing launches instantly.
Synctrayzor 1.1.29 is packaged with Syncthing 1.18.1. From your console it looks like Synctrayzor attempted to use Syncthing 1.18.1 with a config file from a newer version of Syncthing. My guess is that it tried to use the config file from Syncthing 1.26.0 on Syncthing 1.18.1. I suspect that the Syncthing 1.26.0 executable is not in the location Synctrayzor 1.1.29 expected.
Synctrayzor 1.1.29 is capable of running Syncthing 1.26.0, so if you want to run Syncthing 1.26.0 or newer on Synctrayzor 1.1.29 there are two options you can attempt.
You can replace the Syncthing executable at C:\Users\<username>\AppData\Roaming\SyncTrayzor. This should solve your problem and you can keep your config file.
Reinstall Synctrayzor 1.1.29 and allow it to run Syncthing 1.18.1 without your config file, since automatic upgrade is enabled it should upgrade to the current stable release by default which is currently Syncthing 1.26.1.
Special note: When Synctrayzor or Synctrayzor-Portable runs for the first time it will seem as though it shipped with the current stable release of Syncthing, this is because Syncthing will upgrade itself during the startup processes.