The quarantine hotel booking website has reopened just three days before tougher border rules are introduced.
Difficulties with the website were reported since it first went live on Thursday afternoon, but it appeared to have been fixed by Friday night.
UK nationals or residents returning to England from 33 red list countries will be required to quarantine for 10 days in a Government-approved hotel from Monday.
Scotland is extending the requirement for international arrivals from any country.
The cost for a quarantine hotel stay is £1,750 for a single adult.
People face being fined up to £4,000 if they arrive in England without making a booking.
Home Secretary Priti Patel had earlier urged people to “persevere” with the website.