I've noticed on the DropDownDataGrid that the click area does not fill the entire box. The click area seems to be limited to this area:
In other words, if you click towards the edge of the box nothing happens. I would expect to be able to click anywhere in the box to activate the dropdown.
Yes, the DropDown components work fine, but the DropDownDataGrid components have this issue. I am able to reproduce this on your online demos using Brave and Firefox. https://blazor.radzen.com/dropdown-datagrid
It looks likes the area is a bit larger around the dropdown arrow, but elsewhere the click area is smaller. Can you try clicking the bottom left corner?
I have confirmed this is an issue with the same version Firefox, along with Chrome and Edge on two different computers. I guess I have the habit of clicking low on the dropdown because I hit this issue a lot.