These are clearly not the same device, see the major/minor? Another device is detected as a prolific serial converter and is taking the symlink. You need to be more restrictive on the device selection in the udev rule.

-Eric

Hello Eric,

I only have one adapter plugged in, it's a symlink through udev rules.
Something has changed, I need to figure it out. yes I agree the major an minor are different.

Change logging level of the udev daemon with "udevadm control --log-priority=info". Plug out, run "dmesg -Hw", plug in. You should see what is happening perhaps.

-Eric

Oh sorry now I see it! You need to filter the "tty" subsystem in your udev rule, not the "usb" subsystem. What you are interested in is the device that offer serial transfer features...

-Eric

ok, I shall amend the rule and see how it goes. Will report soon.

Just FYI for the people googling this in the future: I had this exact same problem with a CP201x usb-serial adapter. The solution is to change all the "ATTR" references to "ATTRS" in the udev rules. That's it. That's the magic incantation. I hoped this helped someone.
In this case changing ATTR{manufacturer}=="Prolific Technology Inc." to ATTRS{manufacturer}=="Prolific Technology Inc." most likely would have fixed OP's issue.

Also, here's a link to a pile of udev rules at work:
raw.githubusercontent.com/platformio/pla...latformio-udev.rules
It was through examining the differences between those rules and my own that fixed the issue.