Ask to a member of the imaging facility if the objective is not touching the ECi to add adtionnal liquid
Do an autofocus
If the autofocus is not working, use the manual adjustment slider to get closer to the focus of the sample. Always keep an eye on the objective while doing this step to not immerse the objective too much.
Redo the autofocus
Ask a member of the imaging facility to take a look at the alignment of the lightsheet