Konecto vinyl plank floor

We had a friend install Konecto vinyl plank flooring over our existing sheet vinyl and very pleased with job and appearance. A month later during a quick warm spell in April the floor buckled and after investigating a section of the old sheet vinyl has come up from the sub-floor. Lesson learned we should have removed the old vinyl but are there any tips on how to cause the old vinyl to lay back in an effort to avoid removing the new vinyl. The bubble is roughly a 2' x 2' area and it is an old farmhouse where floors are not very level. Furthermore in another 5 to 10 years we will likely remove all and install real wood floors. So I am just trying to get the floor to lay down and avoid the expense of ripping up brand new vinyl plank floors. Any suggestions would be appreciated.