Short answer: a missing Trainer Battle icon on a friend's profile is almost always caused by the "Allow Battle Challenges with Friends" setting being off for one of you, a device clock that isn't synced automatically, or a child account that hasn't had multiplayer features enabled by a parent or guardian. Check those three things in order before assuming something is broken.
Trainer school
Why don't I see the Trainer Battle icon or invite option on a friend's profile in Pokémon GO?
This is a different problem from not being able to battle a friend remotely because you haven't reached Ultra Friend yet — that's a friendship-level limit, and the icon still shows up, it's just greyed out or restricted to nearby. This guide is for when the battle option is missing entirely, for either of you, at any friendship level.
1. Check the battle-challenges setting — on both accounts
Trainer Battles with friends can be turned off per account. In the app, go to Settings → General and make sure "Allow Battle Challenges with Friends" is switched on. If it's off on your friend's account, they'll see a "Player is currently not receiving challenges" message when you try to challenge them — so if the icon is missing on your end, ask your friend to check their own setting too. This is the single most common cause.
2. Sync your device clock automatically
Niantic's own troubleshooting steps for this exact symptom list your device's date and time next. Go to your phone's system date-and-time settings and make sure it's set to sync automatically with your local time zone, not set manually. A clock that's drifted out of sync with Niantic's servers can silently block multiplayer features like battle invites.
3. Child accounts need multiplayer enabled by a parent
If either account is a child account (managed through the Niantic Kids Parent Portal or the Pokémon Trainer Club site), Trainer Battles and other multiplayer features are opt-in. A parent or guardian has to turn on multiplayer access for that account before the battle icon will ever appear — no in-app setting fixes this from the player's own account.
Still missing?
If you've checked all three and the icon still isn't there, Niantic's support team is the next step — this is specifically what their official FAQ article on the topic tells players to do once the three checks above don't resolve it.
Related: this isn't the same as a friendship-level limit
Don't confuse a missing icon with a friendship-level restriction. Below Ultra Friend, you can only battle a friend while physically near each other — the option is still there, it just requires proximity. See Trainer Battles with friends: rules, rewards and remote requirements for exactly which friendship level unlocks remote battling.
If you're trying to build friendships faster so battling unlocks sooner, grab a fresh trainer code with one tap and work through stacking friendship level-ups.
FAQ
I turned on "Allow Battle Challenges with Friends" and it still doesn't show up — why? Check your friend's setting too, not just yours — both accounts need it enabled for either side to see the invite option.
Does this setting affect Nearby Battles against strangers? No. "Allow Battle Challenges with Friends" only controls battles against people on your friend list. Nearby Battles against non-friends use a separate, always-on matchmaking flow for level 10+ trainers.
Will reinstalling the app fix a missing battle icon? Niantic's own FAQ for this issue doesn't mention reinstalling as a fix — it points to the setting, the device clock, and parental controls. Try those first.
Can my friend battle me even if I can't see the icon on their profile? No — the option has to appear for both of you. If it's missing for you, invites you receive from them may also fail with the "not receiving challenges" message until the setting issue is fixed.