Failed to complete OAuth handshake with Google

Dear friends,

I’m running the snap behind a firewall, and I’m trying to set up OAuth with Google. Unfortunately I always get the error below. The network staff tells me that there are no outgoing requests and that the firewall is thus not to blame. Can you help me resolve the issue? Thanks!

Exception while invoking method ‘login’

    at getTokens (/snap/rocketchat-server/1321/programs/server/packages/google-oauth.js:133:25)
    at Object.getServiceData [as handleOauthRequest] (/snap/rocketchat-server/1321/programs/server/packages/google-oauth.js:107:35)
    at OAuth._requestHandlers.(anonymous function) (packages/oauth2.js:27:31)
    at middleware (packages/oauth.js:194:5)
    at /snap/rocketchat-server/1321/programs/server/npm/node_modules/meteor/promise/node_modules/meteor-promise/fiber_pool.js:43:40

Just to confirm what Rocket.Chat version?

I’m on the most recent snap version (0.69.0)