Your channel can only have 200 members. Please note that the total number of members is limited to 200. If you already have 100 members (who joined via links rather than your invitation), you can only manually add another 100. Please accept our apologies if you already have more than 200 members. You are unable to use this feature.
Manually adding members is a fantastic place to start. your channel. It will be easier to get organic users if you already have at least 200 members, rather than 10-15 members.