OAS entered exceeds maximum but it doesn't

Program says my OAS exceeds maximum allowed although the amount entered is the maximum allowed according to your program and Services Canada. I re-entered the amount twice and the amount of tax owed has increased twice. I shouldn't owe any tax. This edition is basic but doesn't even make the cut for basic. I have been with turbotax for years and always trusted it but this year there are serious problems. What is going on?