There may be 2 reasons why your VPS is locked.
Every day at 2:00AM (WEST time), our servers create a daily backup of your VPS. During this period, your management panel is locked to prevent damages in the creation of the backup. This process is completely automatic and should be finished in around 2/3 minutes.
Other explanation is we have locked your VPS for support reasons. To prevent damages in the VPS while we are performing changes, we might lock your management panel.
If your problem persists, please contact support. We will gladly help you fix your problem.