T193470 describes how mapframe maps with images in the GeoJSON code don't display on the mobile apps (ios and Android) or on the mobile website. But what about mapframe maps that do not include such an image? It turns out that these "simple" maps do display on the mobile web site, but do not display on the apps—at least they usually don't.
E.g., here is a page that compares a map that includes an image versus one that has no image.
[desktop link] https://en.wikipedia.org/wiki/User:JMatazzoni_(WMF)/maptest
[mobile link] https://en.m.wikipedia.org/wiki/User:JMatazzoni_(WMF)/maptest
For testing purposes, here are the same maps on test2 wiki, which displays dynamic maps on the page (instead of static maps, like most Wikipedias), and on ca.wiki, which displays static maps and should be the same as en.wiki but we're just making sure.
|the page above on mobile Web||the same page on the iOS app|
So why does the title say "sometimes"
In general, the mapframe maps I've looked at on the iOS app do not display. E.g., maps should appear at the bottom of the info box templates on both these pages, from Korean and Italian Wikipedias, respectively (click the gray strips to open the info boxes in the app):
Mapframe maps that do NOT display on iOS app
- (These do display on mobile Web, btw.)
However, for reasons we do not understand, many mapframe maps do display on Catalan Wikipedia, where mapframe has been implemented for a while now. Here is an example that will, perhaps, provide a clue to the problem:
Mapframe map DOES display on iOS app
image of a mapframe map on ca.wiki that does display in the iOS app (for some reason)
In May Collaboration team released mapframe to277 Wikipedias, including English. This new capability will surely raise the profile and usage of mapframe maps. Please consider this) as you prioritize this ticket and T193470.