The partition 1 that fdisk is complaining about is /dev/sdb1 as to resolving the issue that it's reporting. Well I'm not sure that that is the issue, your system has two "Windows" disks "C:...
I'm in agreement with Corona688, but a little research has shown this to be pretty common with Ubuntu 18.04 - it was there in the Beta and had been reported in some earlier releases as well...
To give us a starting place for your Ubuntu problem, could you post the output from df -h and if possible the output from dmesg this should get us going.