markers missing after upgrade

Strange – when I look in your code, I see that in the header you are enqueuing an old version of javascript needed for the plugin:

<script type='text/javascript'>
/* <![CDATA[ */
var leafletmapsmarker_L10n = {"lmm_zoom_in":"Zoom in","lmm_zoom_out":"Zoom out","lmm_googlemaps_language":"","lmm_googlemaps_libraries":"","lmm_googlemaps_base_domain":"&base_domain=maps.google.com"};
/* ]]> */
</script>

[Please post code & markup between backticks or use the code button. Your posted code may now have been permanently damaged by the forum’s parser.]

with the latest version 3.6.2 this should be

<script type=’text/javascript’>
/* <![CDATA[ */
var mapsmarkerjs = {“zoom_in”:”Zoom in”,”zoom_out”:”Zoom out”,”googlemaps_language”:””,”googlemaps_libraries”:””,”googlemaps_base_domain”:”&base_domain=maps.google.com”,”bing_culture”:”en_US”};
/* ]]> */
</script>

On the other hand I see that some parts of the plugin are already v3.6.2:

/* Maps created with MapsMarker.com WordPress plugin – version 3.6.2 */

did you add something manually to your theme? And: how did you update the plugin? through the plugin update process or manually? Please try downloading the 3.6.2 package from the plugin repository and manually upload all files to your server, overwriting the existing ones.

If that doesnt help, please switch to twentytwelve theme and see if this works. If that also doesnt work, deactivate all other plugin for testing purposes and if it works then, re-activate them one-by-one to find the one which is causing the issue.
best,

Robert

Robert, thanks for the speedy reply.

I have now manually removed and uploaded the lastest plugin version. I disabled all other plugins and switched to twentyeleven.

Here’s the resulting source of the homepage: https://pastebin.com/wMbUG8jY
And of the fullscreen view: https://pastebin.com/nm0rKSSg

strange – don’t really know what is causing this – would need temp administration access so that I could take a look