Jeremy Herve on "[Plugin: Jetpack by WordPress.com] Mobile front page shows on desktop browser"

Installed the Mobile plugin and it seems to work fine on my phone (Chrome).
However, the mobile theme is showing for the landing page on my MacBook as well - in Chrome and Safari.
Click on any link and it's back to the regular desktop theme - it's just the front page that shows the mobile theme.
The site does have a custom (hard-coded) theme so I can see why some tinkering might be needed but Jetpack doesn't offer a host of options.
I encountered this many versions ago and got it half-working with some hacking around but had to give up, am hoping time has seen someone else have the problem and come up with an answer!
The site - http://www.isthismusic.com - is actually running Jetpack Mobile just now but I'll have to tu it off at some point as it's not a great welcome on desktop!

https://wordpress.org/plugins/jetpack/

This could be caused by your caching plugin, WP Super Cache.
Could you try the following:

1. Go to Settings > WP Super Cache > Advanced
2. Check the following option: "Mobile device support. (Exteal plugin or theme required. See the FAQ for further details.)"
3. Save changes
4. Go to Settings > WP Super Cache > Plugins
5. Enable the Jetpack Mobile Theme option there
6. Save your changes
7. Go to Settings > WP Super Cache > Contents
8. Delete all your cache

Let me know if it helps.

Thanks for the prompt reply. I had actually done all this troubleshooting with Supercache in the past so found that the 2 settings above were still enabled. I checked them anyway, and then deleted the cache.
And... now the desktop is ok... but the mobile site is now showing the desktop version all the time! A bit puzzled... I just tued off Supercache completely, but no change...

Do you happen to use another caching plugin on your site, or a caching service put in place by your hosting provider? If so, could you try to tu it off as well?

have checked that Cloudflare is off, and so is the Wordfence caching. Tried tuing off ALL plugins apart from Jetpack, mobile worked apart from the front page, desktop seemed normal. Which confuses things further (had to tu plugins on again for the site to function unfortunately which probably doesn't tell us much more). Supercache is now off permanently...

... and ...
with only Jetpack active, I get - on mobile *and* desktop - the mobile landing page, and the full site for all other pages! (have obviously had to disable the plugin again... sorry, this looks impossible to troubleshoot, had been hoping that it was a common glitch with a simple solution...)

This is definitely a caching issue, but I'm not sure why it doesn't get fixed when deactivating your caching services.

When deactivating Cloudflare and Wordfence, is it possible that some of the pages were still cached in your browser?

I changed browsers and went to a tablet that had never visited the site and got similar results. I know that it must seem like it was a caching problem and I could see no consistency to diagnose. I'm trying a different solution for now, I may need to come back to Jetpack if that has similar results. But thanks for all your help (so far...)

I know that it must seem like it was a caching problem and I could see no consistency to diagnose.

That seems weird indeed. If it's not caching, I wonder if it could be a conflict with another one of your plugins. It might be worth tuing them all off, one at a time, to make sure none of those plugins conflict with Jetpack's mobile detection.

I'm trying a different solution for now

Let me know how it goes!