The City of Ottawa said Monday that problems with the provincial vaccine booking system means nobody could use it to make or move an appointment.
People turning 80 in 2021 or older could move up their appointment for a second vaccine dose in Ontario as of 8 a.m. Monday.
The province blamed a "clinic configuration issue" identified Monday morning as the source of the problem. In a statement to CBC, the Ministry of Health said some individuals were able to book appointments at clinics that didn't have any available, causing an overbooking problem in certain cases.
The ministry said Ottawa Public Health asked it to pause clinic bookings and as of Monday evening, the province was still working to resolve the problems.
As of Sunday night, nearly 39,000 Ottawa residents age 80 or above had a first vaccine dose.
The problems also affect people trying to make an appointment for a first dose through this system.
Pharmacies use different booking systems in Ontario.
Elsewhere in the region, the Eastern Ontario Health Unit said in a tweet people having trouble booking appointments online should try calling instead.