When trying to run some commands, Groovy may lack certain permissions. When this happens, Groovy will refuse to run any commands until these issues are resolved. This is not optional -- Groovy actually requires these permissions to perform the command. You can find the full list of which permissions Groovy requires here.
If you believe the bot has the necessary permissions, be sure to check the channel's role overrides. They are able to override role's permissions in certain channels.
If you are still unable to figure out why Groovy does not have the required permissions, give Groovy the Administrator permission. This will resolve any and all Discord permission issues.