The Bracebridge, in Sutton Coldfield, shut on 15 July due to a lack of staff.
Claire Brough said it was "just getting ridiculous" at what "should be our busiest time of year".
Several other pubs and restaurants in the West Midlands have also said they were forced to close in the past week due to staff self-isolating.
Mrs Brough said the closure meant her business had lost out on about 2,500 people eating in the venue.
With most legal restrictions on social contact lifted in England on Monday, she said this should have been the "perfect time to have a boost to business".
"We have done everything properly, really going overboard to keep everyone safe - and then this happens," she said.
She added they planned to reopen on Saturday but had reduced their menu and would only seat people outside on their terrace.
People who are "pinged" by the NHS Covid app and told they have been in close contact with someone with coronavirus are advised - but not legally obliged - to self-isolate for 10 days.
However, anyone contacted directly by NHS Test and Trace must self-isolate.
But some businesses have warned these rules for close contacts were having a big impact on them.
“Staff shortages put pressure on other workers.” Lawrence Barton
Lawrence Barton, who runs venues including Birmingham's The Loft and Nightingale Club, said the impact of staff self-isolating after the easing of restrictions was like "taking five steps forward and 10 back".
He said while his businesses had not completely shut, some work was scaled back as an average of five staff were self-isolating each week.
"It is an absolute pain, it puts a strain on people who are left there working. It was fraught on Saturday with five people down," he said.
O'Neills on Broad Street, which shut on Sunday and Hockley Social Club which closed on Monday until 30 July are among other venues hit.
Meanwhile, the Hare and Hounds pub in Kings Heath said on Facebook it was "difficult and devastating" to have to close until 28 July after a staff member tested positive for Covid.
The government has insisted isolation remained the "most important action" people can take to stop the spread of the virus and businesses should help employees to do so.
