After installing this plugin all markers from events are not being shown anymore.

In fact it just kills all markers of everything. Not good.

The plugin hasn't received an update in over four years, even after being transferred to a new developer. I would recommend looking for an alternative plugin that is actively maintained and regularly updated to avoid potential causes of issues or conflicts.

See if this plugin does what you want https://umod.org/plugins/tc-map-markers

Thanx. I will check it out.