Please make sure you are using the correct master password by checking the caps lock off. Also, please try copy and pasting your master password in the password field to check if that works. If the problem persists, please drop us an email at firstname.lastname@example.org so that we can help you better.
On which all devices (along with OS version) are you using Enpass?
Which Enpass version are you using on each device?
Which cloud services are you using?
Does your master password contains any special character?
Are you able to access all Enpass data on any of the devices?
Thanks for your co-operation.