When you boot Ubuntu got this error message with no response from keyboard input. Below it is says Wait to continue, press S to skip mounting, or M for manual recovery.
Looks like the UUIDs of some of your partitions have changed. And your /etc/fstab specifies the old UUID so it is not able to mount EFI and some other partitions during boot process.
Open a Terminal, run blkid to get the list of UUIDs for all your block devices/logical volumes. Then edit fstab file:
$ sudo vim /etc/fstab
Make sure the UUIDs of partitions/block devices are correct, if not, update and save.
NOTE: If you don't like UUID, just use traditional block device, e.g. /dev/sda2 instead of UUID=x.