First, what version of ConfigMgr are you actually running? ConfigMgr Current Branch or ConfigMgr 2012?
Next, last login timestamp is a value pulled from Active Directory and because of the way it is populated in AD can be up to 14 days old so this is by design and expected and not in any way indicative of an issue in ConfigMgr. See https://video2.skills-academy.com/en-us/archive/blogs/askds/the-lastlogontimestamp-attribute-what-it-was-designed-for-and-how-it-works for more info.