Why does it say i have unbuilt objects when i click landscape

anonymous_user_0068f50d
Wed, 07 Oct 2020 14:41:58 +0000
Rendering

I have rebuilt my lighting and all looks good, no rebuild lighting message appears, however when i then click the landcape tool i get greeted with the message “lighting needs to be rebuilt” (2087 unbuilt objects)

I repeat the process and happens every time

If someone could shed some light it would be appreciated

Kind regards