I cannot get immigration working in Hidden Springs.

I use NRaas Immigration Gauge and most worlds seem decent with a setting of 1 (0 is none, 2 seems to require massive demand before anyone new is admitted). Sunlit Tides uses 1 for a couple of days then back to 0 before the council starts complaining of lack of housing (I built a dozen or so new houses, from two room hovels to six bedroom mansions, all were occupied in a couple of days and the council was still complaining).

But on Hidden Springs a setting of 2 produces endless messages about not enough pressure to allow immigration, while a setting of 1 produces these two messages alternating every 10-15 minutes -






What does it want me to do?

If you want to force immigration, use the Rapid Immigration setting and set it to the number of households you want to fill.

Otherwise, what the Immigration Gauge system 'wants' is to be left alone until the gauge hits the number you have set.
Each cycle (the length of which depends on your SP speed settings), different things will contribute to immigration pressure - one point for each career missing a boss, ten points for an unsuccessful flirt scenario, ten points for each time the pregnancy manager cannot find any valid sims, and ten when the population of each age stage is unbalanced.

The common default of 10 points means the gauge is best set to 10 or higher, depending on whether you want immigrants immediately or if you want pressure to build for longer. Your speed settings may be too fast if you're seeing the notification multiple times a sim-day, or the gauge may simply be on too low of a number.

Some worlds may not create immigration pressure for a while, depending on the make-up of the population, their romantic successes, career coverage, so on.
This is a good thing - the immigration gauge is intended to create sims when they're needed, rather than at random.

Well, I'm not looking to force immigration, only to find settings that allow a trickle when needed. (SP speed is slower than default, lifespans are longer, for a leisurely game.)

But those messages confuse me. One seems to say "pressure is 0, we require 1 to allow immigration". Fine. Then later that day the message seems to be "pressure is 1, we require 1, we want more than 1". If I set the gauge to 2 there is never any immigration, and occasional messages say "pressure is 1, we require 2". I'm just trying to interpret what these messages are telling me.

In Sunset Valley I rarely see any messages about immigration but occasionally see a previously empty house now occupied by an unfamiliar sim, so assume everything is working fine there and settings are balanced. This is what I hope to achieve on other worlds.

Personally I never used SP before and not familiar with it so I can't help here. But I can recommend other mod that alters immigrant population, which is NRaas Traveler. From there you can disallow immigrants from certain worlds, change the chance of leaving or restrict immigration completely.

The thing I know about SP is that you should toggled off the default Story Progression from the settings tab. Plus there should be a setting in the mod that disallows pop-up notifications.