Some themes/plugins make use of content preloading. This can break the loading of the OUM map. In this rare case please disable preloading for the page where you have integrated the map.

Alternatively you could manually trigger the oumMap.invalidateSize() method after the content has been loaded. Since version 1.3.3 this can be added under Open User Map > Settings > Advanced > Custom JS.

// Javascript, to be triggered when the page is loaded

oumMap.invalidateSize();

This will reinitialise the OUM map.