UM3 finishes print right after heating up

[ohms 1]

Hi, I updated to cura 2.7 from 2.6 and now when I start a print, it only heats ups the build plate and hotend, then immediately says print finished. Tried going back to 2.6 and now it is doing the same thing there. I can see as it is heating up that there is no estimated print time, only job name and printing time of 00:00:00

[ohms 1]

looks like it was actually the new .8mm core I installed. I changed back to the .4mm core and it is printing fine. Now I just don't know why it won't print with the new core

[CarloK 39]

Which firmware are you running on the printer?

What material are you printing in the 0.8mm nozzle? Is it original Ultimaker or a generic material?

The supported nozzle sizes and materials are a combination stored in material profiles on the printer. Cura v2.6 and earlier did overwrite those material settings on the printer. You might have to install Cura 2.7 again, this fixes the profile overwrite problem. Verify you have firmware v3.7 on the printer and do a factory reset on the printer in order to restore the original printer's material profiles.