Hi there, welcome to the forum!
I’m not sure how your app connect works, but if it is asking for a refresh token that implies there should be somewhere an expiration parameter.
Refresh tokens are common in OAuth 2.0 protocol, and usually involve redirecting the user to an authentication page, let me know if that is the case, you may be able to completely configure the App connect to automate the OAuth 2.0 process.
Please note that in box only the OAuth protocol will give you a refresh token.
If in your connect designer the refresh token is not mandatory, then you should be able to just use the developer token directly in the access token.
You could also manually do the OAuth process and get both the access and refresh tokens. The easiest way to do this would be to follow our postman quick start guide, which will give you these tokens.
If you have access to other tools a script and help you here to, for example check out our Python OAuth Template, this will save the tokens on a local file.
If you’re not using OAuth you can request a token directly to the API, for example using curl for a Client Credentials Grant (CCG)
curl --location 'https://api.box.com/oauth2/token' \
--header 'Content-Type: application/x-www-form-urlencoded' \
--data-urlencode 'grant_type=client_credentials' \
--data-urlencode 'client_id=h5z...qi' \
--data-urlencode 'client_secret=Tq...A38' \
--data-urlencode 'box_subject_type=enterprise' \
Will result in:
You can also investigate if the app connector supports anything else than OAuth.
Let us know if this helps
PS: just noticed that there is a box connector for IBM App connect. This might be easier to use.