If you're issue related to connecting a feed then please see our Troubleshooting FAQ.
As of Momento 3.5 the free version of Momento is restricted to adding 1 feed. This restriction is the number of feeds you can have in Momento, irrespective of whether the feeds are connected or disconnected.
If you're a Momento Classic user using the free version of Momento 3, and have imported your existing data, then all feed connections will have been disconnected.
If you have imported 1 or more feeds then you will only be able to connect 1 feed and you won't be able to add any new feeds.
Additional Feed Connections
Additional Feed connections are only available as part of Momento Premium.
If you have previously purchases additional feeds in Momento 3.4 or earlier you can restore this functionality via the 'Restore Purchases' button on the 'Premium' settings screen.