Here're 3 easy steps to help you unblock a time:
STEP 1: Login to your Appointy admin area.
STEP 2: Under Calendar → Day View → Staff option on left side → Under Staff name, Click on Block Day/Time

STEP 3: You will see the page with Regular Work Schedule, Future Unavailability and Staff Details tabs. This is where you can manage the availability/non-availability of the staffs. Go to Future Unavailability tab.

You can hover the mouse on any times (that you want to delete/unblock) to get the trash icon. If the events were blocked by Google calendar linked in Admin account, then repeat the above steps for all Staff.
Should you need any assistance, please reach us at contact@appointy.com, and our support officers will be happy to help.