# Cura 3.5 doesn't launch repeatably

When I was notified by Cura that 3.5 was out, I looked at the changelog, and I installed the new version. It worked normally for a time, until once when I went to launch it and cura.exe forever sat idle in task manager doing nothing. I reinstalled Cura 3.5 and tried again.

That then worked for some time, maybe another couple days, and then the same thing happened again. Rince and repeat, maybe for a few more cycles. Now, Cura 3.5 doesn't like to do anything even fresh out of the box. Restarting the computer does nothing.

I've looked at the cura.log file in AppData/Roaming/cura and found a peculiar line:

... 2018-10-10 21:49:33,591 - INFO - [MainThread] UM.VersionUpgradeManager._upgradeFile [369]: Upgraded .\fdmextruder+%232_user.inst.cfg to version 4000005. 2018-10-10 21:49:33,605 - DEBUG - [MainThread] UM.Backend.Backend._logSocketState [178]: Socket state changed to Listening 2018-10-10 21:49:33,650 - INFO - [MainThread] UM.Backend.Backend.startEngine [74]: Started engine process: C:\Program Files\Ultimaker Cura 3.5\CuraEngine.exe 2018-10-10 21:49:33,652 - DEBUG - [MainThread] UM.Backend.Backend._backendLog [94]: [Backend] Calling engine with: ['C:\\Program Files\\Ultimaker Cura 3.5\\CuraEngine.exe', 'connect', '127.0.0.1:49674', '-j', 'C:\\Program Files\\Ultimaker Cura 3.5\\resources\\definitions\\fdmprinter.def.json', ''] 

It looks as if the issue is when the Cura GUI tries to connect to its backend slicing engine. Is my analysis correct? Is this a known issue/is there a known fix?

I'm going to try to report this to Ultimaker if nothing comes up here.

• This should be mentioned at the Ultimaker forums, not here. I have had similar experience with an older version of Ultimaker Cura. Removing the appdata and re-install fixed it for me. Look at this topic. – 0scar Oct 11 '18 at 6:01
• Yea... that seems to work. Any word on why the issue exists in the firstplace? – ifconfig Oct 11 '18 at 6:22
• File bug reports. Or, to be precise, first check for existing reports over at Cura, then file. – Carl Witthoft Oct 11 '18 at 15:22
• Yea... I'm in talks with NA support now. @0scar's solution worked for a few hours, or as long as I keep the cura window open. – ifconfig Oct 11 '18 at 15:39

A workaround, but not a definite solution, is to remove the settings (on the Windows platform these files are located in AppData/Roaming/cura) that Ultimaker Cura uses and remove prior installations and do a fresh re-install of 3.5 and see if this works. Just rename the directory to e.g. AppData/Roaming/cura_old, this way you can always go back.