Error: Failed To Decrypt Data (Invalid Passphrase?)

I assume service status was from Task Manager Services tab or Services tool linked on there.
That tool could attempt to add some logging to file after Duplicati.WindowsService.exe launches Duplicati.Server.exe. Duplicati.WindowsService.exe shows how to do that at initial service install, however the Windows Services tool lets you amend a startup line (Path to executable) later.

I don’t know if you also run Duplicati.TrayIcon.exe. If so, a full set of processes is shown under
[SOLVED] Is it ok that I see 5 processes of Duplicati in Windows Task manager?

What happens? Is there an error message (like you get with service down), or does it sit silently?
How to do a hard refresh in Chrome, Firefox and IE? might help if it gets stuck. If it can’t, logs at Duplicati level for web server startup and browser activity are pretty minimal, but maybe can help.

The netstat command can show if anything is working at the usual Duplicati port (probably 8200). Because you run a service, you probably need an Admin prompt in order to look at Duplicati use:

C:\>netstat -ano | findstr 8200
  TCP    127.0.0.1:8200         0.0.0.0:0              LISTENING       4704
  TCP    127.0.0.1:8200         127.0.0.1:57070        ESTABLISHED     4704
  TCP    127.0.0.1:8200         127.0.0.1:57071        ESTABLISHED     4704
  TCP    127.0.0.1:8200         127.0.0.1:57072        ESTABLISHED     4704
  TCP    127.0.0.1:8200         127.0.0.1:57073        ESTABLISHED     4704
  TCP    127.0.0.1:8200         127.0.0.1:57074        ESTABLISHED     4704
  TCP    127.0.0.1:8200         127.0.0.1:57075        ESTABLISHED     4704
  TCP    127.0.0.1:8200         127.0.0.1:57401        ESTABLISHED     4704
  TCP    127.0.0.1:8200         127.0.0.1:57402        ESTABLISHED     4704
  TCP    127.0.0.1:8200         127.0.0.1:57554        ESTABLISHED     4704
  TCP    127.0.0.1:8200         127.0.0.1:57567        ESTABLISHED     4704
  TCP    127.0.0.1:57070        127.0.0.1:8200         ESTABLISHED     71936
  TCP    127.0.0.1:57071        127.0.0.1:8200         ESTABLISHED     71936
  TCP    127.0.0.1:57072        127.0.0.1:8200         ESTABLISHED     10664
  TCP    127.0.0.1:57073        127.0.0.1:8200         ESTABLISHED     10664
  TCP    127.0.0.1:57074        127.0.0.1:8200         ESTABLISHED     10664
  TCP    127.0.0.1:57075        127.0.0.1:8200         ESTABLISHED     10664
  TCP    127.0.0.1:57401        127.0.0.1:8200         ESTABLISHED     19088
  TCP    127.0.0.1:57402        127.0.0.1:8200         ESTABLISHED     19088
  TCP    127.0.0.1:57554        127.0.0.1:8200         ESTABLISHED     19088
  TCP    127.0.0.1:57567        127.0.0.1:8200         ESTABLISHED     4704

C:\>