certificate error with android

I compiled a mobile apk to submit to customers for testing, and their writing that when trying to install the apk on their devices, on adb, and on the emulator, they get a certificate missing on AndroidManifest.xml. Do i have to add a certificate when outputting to android? How do i add a certificate to androidmanifest.xml on construct 3?

thank yous

No need to add certificates.

but ive tested and apks compiled with release dont work on my androids, but debug compiled apks do. The debug compiled apk that i sent my customers doesnt work with their android devices, the game issues the stopped working error.