Sometimes a new version of FlexiTime is released, but your browser keeps hold of an older version that is is storing locally on your PC. This is called caching, and generally it is a good thing. It means that larger applications like FlexiTime are very fast to load. However it can occasionally prevent you from running the current version of FlexiTime after an upgrade.
If you have an old version of FlexiTime you should clear your browser's cache. Here's a webpage that has an excellent description of how to do it in a range of different browsers: