I have multiple SwOS devices (2x CSS326-24G-2S+, 1x CRS305-1G-4S+ in SwOS mode). All are running the latest available version 2.17.

Today I recognized that I cannot modify the VLAN settings for either of the CSS326. Each time I modify a setting, the "Pending changes" indicator appears below the table, but the "Apply all" button does not respond to clicks. I tried modifying VLAN mode, tried modifying VLAN receive, tried modifying default VLAN ID -- everything gets the same behavior, regardless of the port I try to modify. I tried modifying a port that doesn't have link: no success. I tried disabling a port first, then modifying it's VLAN settings: no success

Modifying VLAN settings on the CRS305 still works fine.

I am using VLANs on 8 various SwitchOS devices (including 5 CSS326 switches) and have never had any issue making VLAN changes. Do so rather regularly.
What are you attempting to change?

I have a couple of WLAN access points connected to a dumb PoE switch. That PoE switch is currently connected to an "only tagged" port on one of my CSS326. I want to change that port from "only tagged" to "any", because that makes provisioning new APs easier.

I also have Access Points that use VLANs for each SSID and untagged for management, so I understand what you need to do. Those ports are already set to Any, but I took a VLAN only trunk and changed it in one of my CSS326 switches (SWOS version 2.17) to any and saved it and it saved properly. I then changed it back to VLAN only and again it saved properly.
First suggestion is to try a different browser, and if that does not help, grab a screen capture of both the VLAN and VLANs tabs and post them here.

Tried multiple browsers. Same outcome :-/

The dumb PoE switch is connected to port 5 of my upstairs CSS326.

CSS326 upstairs: CSS326 downstairs:

You can't use VLAN 0, this is not part of 802.1Q standard, and the web interface clearly shows it with the red font.

Switch documentation is also clear about what values are supported:

Default VLAN ID (integer: 1..4095; Default: 1)

https://help.mikrotik.com/docs/spaces/S ... ANandVLANs

Well, not that clearly. Plot twist: I'm colorblind

Thanks a lot. I never set the VLAN manually to 0, but kept it at whatever the default was years ago.

Yep, VLAN 0 would be an issue. Also avoid using VLAN 1. Some devices treat VLAN 1 as something special - often with unpredictable results.

Yep, VLAN 0 would be an issue. Also avoid using VLAN 1. Some devices treat VLAN 1 as something special - often with unpredictable results.

Just in case, the first two of the twelve rules of the Mikrotik Club are relevant :
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