Sometimes there are situations when not a single administrator appears in the space.
If you use the access setting through Groups, go to Groups (from the top-left menu, section Users -> Groups) and define the administrators of the required spaces by creating a SEPARATE group for them.
If you are not using Groups, then:
Leave the space to which you have lost administrative access by clicking on yourself in the user panel of this space (on the right);
Enter the administrative section of Space (ATTENTION, this is the second item of Space in the menu on the top left);
From this section, select the space that you left in step 1 and rejoin;
You now have administrative access to the space again.