It's not a continuous 24/7/365 process. They have a drilling season each year, I believe about 6-8 weeks, have drilled at 2 different sites and been interrupted by the pandemic.
Getting supplies such as food and shift changeovers?
International travel was not easy nor reliable during the pandemic, with many borders de facto closed or severely restricted, with quarantines, tests, etc.. needed. The drilling season involves moving an international team from each of their home countries to Greenland, then back again a few weeks later. So practically impossible to make sure the drilling season could happen with the crew required and then get them home again.
Every country I know of had special exemptions in place though, after the first few weeks of panic, for those who could supply credible written explanations.