Minecraft Bedrock on Nintendo Switch, can't do Realms

Have you an active Nintendo Switch Online Subscription? I ask this because I found the following Q/A on Minecraft Nintendo Switch FAQ:

Can I play Realms on this edition?

Yes, Realms is available on the Bedrock edition of Minecraft for Nintendo Switch. To play online on a Nintendo Switch, you need to have a Nintendo Switch Online subscription, so this is a requirement for playing on Realms. More information about Nintendo Switch Online can be found here.

Furthermore, can you post the entire error message (better a screenshot/photo)?

Hello,

Do you have the Nintendo "parental control" enabled? https://www.nintendo.com/switch/parental-controls/

Are you authorized to buy things in Xbox Live? https://account.microsoft.com/family/

I don't have any parental controls on my Switch, and I think I can buy stuff on Xbox Live. I'm set as an organizer on the family group so I don't think there should be any issues with children's permissions.

Hello,

Do you have the Nintendo "parental control" enabled? https://www.nintendo.com/switch/parental-controls/

Are you authorized to buy things in Xbox Live? https://account.microsoft.com/family/

The Bedrock version of Minecraft is crossplay enabled for Windows 10, Mobile, Xbox One, VR and Nintendo Switch.

Realms is a mutliplayer server made for the Bedrock edition. There is different options for realms that determines how many people can play at the same time. Highest is 10 people excluding the owner. They are available 24/7 if the realm is payed for.

To play online, you'll need xbox gold membership. For the Minecraft version i think you'll need the bedrock editon (which is the one for Xbox, windows 10 and Nintendo switch that just have "Minecraft" in the title (it doesn't say bedrock edition)) and
to join a realm you need to get an invite from the person that has created the realm