Have basic 2 line 4 sets on a Strata CHSU40, only ext 200 rings and flashes green on incoming calls.
Other sets only flash, would like to have all phones ring.
Tried programming in section 205 for each of the DNs and each of the lines to 222 (for ringing) no change.
Is there an option for Day Ringing group? or another field I need to program.

In Network eManager go to Trunks/Trunk Assignments and then the DIT tab and remove the Day1,Day2 and Night destination of 200.
This will make the system look at the line keys ringing assignments on each handset with a CO line key.

If I don't have eManager, can it be programmed by a phone like the DKT3020?

Yes you can using program 310 and
FB 01 for day 1 destination change "dialing digits" to "no data"
FB 02 for day 2 destination change "dialing digits" to "no data"
FB 03 for Night destination change "dialing digits" to "no data"

Perfect, that did it.
Thanks Carl.

1 other question: Under "Dialing Digits" it was set to : Dest = 600 for Day 1 & 2, & Dest = 601 for Night. Which when calling 600 or 601 rings at ext 200.
If I want to add another ext to ring, where do I add the ext to this "group".
Again programming is from the phone.

Well 600 and 601 could be Pilot DN, Hunt Group DN, Phanton DN or a Multi Call Group DN so it is going to be difficult to know without the eManager software.
If you are wanting additional handsets to ring for lines 1-4 with "no data" as advised earlier then you do it by adding line keys to the handsets and assigning them to ring.

I would put money on it being a Multiple Call Group. In a pinch I have added an extension to a MCG using phone programming, but it is not easy.

I agree they are not the easiest to do via a handset but do-able if you already know how they work and are configured.