Problem with mounting File Systems from External Drives

some time ago I set up my Ubuntu to mount external drives always on the same mountpoint. To do that, I mounted according to the UUID, e.g. from my fstab:

UUID=b949cee0-9e93-44c1-b3eb-1857cf5c1167 /media/b949cee0-9e93-44c1-b3eb-1857cf5c1167 ext4 nofail,auto,noatime,rw,user 0 0UUID=17fbaabc-84e1-49a5-aebf-e14dfd1f5502 /media/17fbaabc-84e1-49a5-aebf-e14dfd1f5502 ext4 nofail,auto,noatime,rw,user 0 0

I did so when I used a non-powered (i.e. it doesn't have a power plug), 4-port USB hub: I connected the drives to the Hub, and the Hub is connected to the computer.

I thought that the UUID is ummutable, and that my drives would be mounted at the same mountpoint all the time (which in my case for some reason I named with the UUID as well).

However it happens that when the drives are attached to the USB hub, they are mounted. When they are NOT attached to the hub but are connected directly to the computer, they are not detected at all. Not only the are not mounted, but also when doing lsblk, they don't show up.

How can this be possible? Any hints?

EDIT:

Ubuntu Version:

DISTRIB_ID=UbuntuDISTRIB_RELEASE=18.04DISTRIB_CODENAME=bionicDISTRIB_DESCRIPTION="Ubuntu 18.04.5 LTS"NAME="Ubuntu"VERSION="18.04.5 LTS (Bionic Beaver)"ID=ubuntuID_LIKE=debianPRETTY_NAME="Ubuntu 18.04.5 LTS"VERSION_ID="18.04"VERSION_CODENAME=bionicUBUNTU_CODENAME=bionic

Here is the output of lsusb:

No Drive Attached:Bus 001 Device 002: ID 8087:8000 Intel Corp. Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hubBus 003 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hubBus 002 Device 004: ID 8087:07da Intel Corp. Bus 002 Device 003: ID 046d:c52b Logitech, Inc. Unifying ReceiverBus 002 Device 002: ID 046d:c52b Logitech, Inc. Unifying ReceiverBus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hubOne Drive Attached (no hub attached)nardo@myserver:~$ lsusbBus 001 Device 002: ID 8087:8000 Intel Corp. Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hubBus 003 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hubBus 002 Device 004: ID 8087:07da Intel Corp. Bus 002 Device 003: ID 046d:c52b Logitech, Inc. Unifying ReceiverBus 002 Device 002: ID 046d:c52b Logitech, Inc. Unifying ReceiverBus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hubOne Drive attached through USB HubBus 001 Device 002: ID 8087:8000 Intel Corp. Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hubBus 003 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hubBus 002 Device 004: ID 8087:07da Intel Corp. Bus 002 Device 003: ID 046d:c52b Logitech, Inc. Unifying ReceiverBus 002 Device 002: ID 046d:c52b Logitech, Inc. Unifying ReceiverBus 002 Device 006: ID 1058:25a2 Western Digital Technologies, Inc. Bus 002 Device 005: ID 1a40:0101 Terminus Technology Inc. HubBus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub

Thanks!