Stuck on Installing a custom recovery

I can’t get past the TWRP stage;

Uploading RECOVERY
RECOVERY upload successful

Ending session...
ERROR: Failed to receive session end confirmation!
Releasing device interface...

I then tried to install the vendor file as per docs;

adb sideload VENDOR-27_ARI9/vendor.img 
adb: sideload connection failed: closed
adb: trying pre-KitKat sideload method...
adb: pre-KitKat sideload connection failed: closed

What do I do next? Did TWRP install but just fail to close handshake?



Regain your privacy! Adopt /e/ the unGoogled mobile OS and online servicesphone

Ok took me ages to get OEM setting to appear.

mental. I hadn’t connected my phone to the wifi as yet.

next steps