Follow Up Boss won't connect
What each connection error means and how to get Follow Up Boss connected to Trevy.
Updated October 16, 2026
Trevy connects to Follow Up Boss in one of two ways. The main way is the Sign in with Follow Up Boss button: you sign in to Follow Up Boss, approve Trevy, and land back in Trevy connected. The other way is Use an API key instead, where you paste an API key from FUB. Both are on the first step of setup and in Settings → General → Connections.
If you're an agent on a team, you don't connect FUB yourself. Your Connections card shows "Connected via team leader".
Before you start
Connect as the Follow Up Boss account owner. To send email, Trevy adds its own custom fields to your FUB account, and adding a custom field takes the owner. If someone else connects, Trevy can't finish setting up sending and asks you to reconnect as the account owner.
Errors after signing in with Follow Up Boss
"Trevy wasn't approved in Follow Up Boss, so it isn't connected." Trevy was declined on the Follow Up Boss approval screen. Click Sign in with Follow Up Boss again and approve Trevy.
"That sign-in took too long or started in another browser. Try again." A sign-in has to finish within 15 minutes, in the same browser it started in, while you're signed in to Trevy as the same person who started it. Start again from Trevy and finish in one go.
"Follow Up Boss didn't finish connecting. Try again, or use an API key." FUB turned down the last step of the connection. Try once more. If it fails again, click Use an API key instead.
"Couldn't reach Follow Up Boss just now. Try again in a minute." FUB didn't answer. Wait a minute and try again.
"Signing in with Follow Up Boss isn't available here. Use an API key." Sign-in isn't available for your Trevy, so connect with an API key.
Errors when you use an API key
To find your key, log in to Follow Up Boss, go to Admin → API, and copy your API Key. Paste it into the API Key box and click Connect & Continue during setup, or Connect in Settings.
"API key is required" The box is empty. Paste your key and try again.
"Invalid API key. Please check and try again." FUB didn't accept the key. Copy it again from Admin → API and make sure you pasted all of it, with nothing extra before or after it.
"Couldn't reach Follow Up Boss just now. Try again in a minute." The key worked, but Trevy couldn't find out which FUB account it belongs to. Try again in a minute.
"Failed to connect to Follow Up Boss" Something unexpected went wrong. Try again. If it keeps happening, email support@trevy.io.
Once you're connected
In Settings → General, Follow Up Boss shows a green dot and its button changes from Connect FUB to Reconnect (or Update API Key). Connecting is also when your free trial starts, if your FUB account hasn't had one: see the free trial.
Connecting doesn't send anything yet. Next, set up sending through Follow Up Boss.
If Trevy was connected and later says Follow Up Boss didn't accept its connection, see Follow Up Boss didn't accept Trevy's connection.