UPDATE: It before said:
An error occured while loading the launcher!
Unable to load DLL 'CSteamworks': The specified module could not be found. (Exception from HRESULT: 0x8007007E)
Stacktrace: at Steamworks.NativeMethods.SteamAPI_InitSafe()
at CTLauncher.Main.InitSteamAPI() in F:\VS2015\Projects\CTLauncher\CTLauncher\Dialogs\Main.vb:line 638
at CTLauncher.Main.Main_Load(Object sender, EventArgs e) in F:\VS2015\Projects\CTLauncher\CTLauncher\Dialogs\Main.vb:line 60
I deleted those items in the local files and replaced them with the same original items from download folder.
It now says:
The specified Nuclear Throne is invalid (does not exist or does not contain NuclearThrone.exe)!
I did switch it back to normal gameplay for a bit. Then, after that, I opened back to the mods beta to test the launcher; then the errors ocurred.
...it still won't update, though.