When you take in new members, the system does not fully update all dependencies with their ideology. One example is getting a member of an ideology you did not have before and trying to make them a specialist. You will be able to choose the specialist but can not start the ritual because "not a member of any colony ideology". This is not fixed by save + load but seems to fix itself after some time. It feels like there is not a trigger on member join but instead just a time based check or similar to update these things.
Role select: https://steamuserimages-a.akamaihd.net/ugc/1841409905600255784/4F912AB61143CA0A78BBB7604AE1AD07D85A021E/
Ritual error: https://steamuserimages-a.akamaihd.net/ugc/1841409905600252885/10179FFDF07BEAA424796C1462B60BAFE645B608/
Ideology not counted for colony: https://steamuserimages-a.akamaihd.net/ugc/1841409905600254973/96A0C905414A27D1DAFF58C4DD7AA65E0BDB6FBB/
I do not know when these things update, but right now you have to wait for a mysterious time until the game sees the ideology of the colony member as a colony ideology and you can use their specialist. I remember having issues in the past with creating moral guides just after I accepted my 3rd member into the colony with the game still saying I only got 2 members, but this might have been changed with the first multi ideology buff patch.
Both DLCs, no mods used.
Thanks for the report. Are you able to give them this role after a short time of letting them be in the colony, rather than immediately? If not, it could simply just be that like with the moral guide, you need 3 colonists in your colony to be of that ideo before it 'counts' the ideo as a colony ideo.
Part of the reasoning behind this is taking in a group of refugees that could possibly outnumber your own colony's population and while they are there, it would flip the ideology of the colony to that one, causing havoc.
For all I know there is just some time involved until it works. I did not test the exact time yet (so far I just wait randomly and try again later), but refugees and visitors can be in your colony for a rather long time and I've never had it flip my main ideology. I think the time for the game to understand that the prisoner that just joined your colony brought a new ideology is shorter than the max time refugees have stayed with me. I always thought the game just distinguishes between your own members and guests for those checks. Having a time involved here seems rather unclean and error prone and leads to situations like in the screenshot, where I clearly have one of those people in my colony (since I can select their role) but it says I do not.
As a sidenote: You can also indeed assign guests roles though, if you had 1 of their ideology as a true colonist before, since that is the needed condition.
I did not understand this part:
Quoteyou need 3 colonists in your colony to be of that ideo before it 'counts' the ideo as a colony ideo.
You just need a single pawn of a new ideology in your colony to count that ideology as an ideology of your colony. It just takes some unknown amount if time after that person joined your colony for the game to fully accept that. The count of 3 is solely for the need of a moral guide, their religious buildings and ritual mandatoriness.
Thanks again for the report, I'll file this one away!