Always on display - multiple time zone option disappeared

[George2017]

One if my favorite function has disappeared from my Galaxy S7 Edge (dual sim)
It has been working properly, displaying local time of 4 different cities, but today right after I crossed time zones on highway between EST to CST, the customizable multiple time zone layout has disappeared. I am on Telus' network in Canada. Any suggestions?

[Abd53]

check the AOD settings

[George2017]

of course I did before I noticed that the multiple time zone layout went missing.

[George2017]

It was OK until last night, and it has happened again. I can't even select the last layout in the second last row, the APPLY button is grayed out. See the pics when it worked properly, and now... Any suggestions?