maven is not interested in the region

8 watchstone, I'm doing t9 maps and still can't run in any region maven . How do I launch a Maven beacon?

It's hard to say exactly what the problem is without more information.

Step 1: Do you have the Maven's Beacon? You should have gotten it around the same time as your first Watchstone (maybe the first map you run in a region that has a Watchstone socketed?) After you get the Maven's Beacon, you just need to talk to Zana, and then touch the Map Device. This will cause you to "install" the Maven's Beacon in your Map Device. By default, it will always be turned "on". There's not a whole lot of reason to turn it off. But obviously Maven will not Witness any boss fights while it is off.

Step 2: How many Watchstones do you have socketed into regions, and where are they? Maven requires 1 Watchstone socketed in for the 3-boss fight, 2 watchstones for the 4-boss, 3 watchstones for the 6-boss, and and 4 watchstones for the 10 boss. The maps also have to be the appropriate tier. Higher is OK too. So you can do 3-watchstones in on a T13 map for the "2-watchstone" fight, that's fine.

You can move watchstones around whenever you want with no penalty. You will need to do this if you want to maximize Maven witnessing while also progressing your Atlas by killing Conquerors to get more Watchstones.

So, to summarize, if your 8 watchstones are spread out, 1 stone in each region, Maven will never be interested again after you do the 3-boss fight in that region. You have to double-up some Watchstones (or just keep progressing your Atlas to earn more of them).