Fixes for the things that most often go wrong.
Your email address has not been confirmed. Open the link in your confirmation email first. This is a different message from a wrong password, on purpose.
Claim links expire after 14 days. Any band owner can resend one from the Members page.
An admin has disabled the account. It takes effect immediately, everywhere. Contact whoever runs this install.
You need to be its owner, or an agent whose representation has been approved. A request that is still pending gives you no access yet — see Representing a venue.
Only bands you have an approved connection with, with slot requests enabled, can be booked into a date. That is the band's consent to a confirmed gig landing on their calendar. Connect with them first, or book them as an off-platform act by typing the name.
A venue or agent you are connected to booked you into one of their dates. Turn slot requests off for that connection to stop it — see Booking and agents.