For months I had trouble updating my Moto G4 with a pending security update. I couldn’t find any help online. I complained to Motorola support. No response. My phone said to turn off my Data Saver. That wasn’t the problem because it wasn’t on.
My solution was to just ignore the update screens, constantly pressing “Not Now.” I finally had enough of that and started looking again for a solution. Here’s what fixed it for me:
Settings / Apps / Show System / Moto Update Services / Data Usage
Turn on “Background data”
Turn on “Unrestricted data usage”
Settings / About Phone / System Update
From there it should upgrade.