Thanks Timo. You're right.
From my side, I think I figured it out. My device (Surface Go 3) doesn't have a GPS chip. So if it worked before, the system would pick my location from connections to wifi or to cell towers. But recently, I moved to a wonderful but remote-ish beach in Madagascar. I'm guessing, with little traffic, maybe wifi and towers aren't plotted on the system yet.
Plus, I'm not 100% certain I ever tried "location" on Diarium on my laptop. Though I have on my android, and I might have mixed that up.
My little work around: on Diarium, if I make an entry on my laptop, I can go back later and add the location to the entry from Diarium android app.
Sorry to waste your time with my confusion.
Keep up the good work. I like your products.