Hi and welcome to JustAnswer,Thank you for the question and your patience. Should you still need assistance for information purposes only...Initially, yes as it is automatically switched off when fully charged.
More importantly, Lenmar prescribes that "...Typically, you will need to recharge them at least 3 times to reach peak performance..." as may be viewed HERE.
Bear with us, keep charging for an extended period of time (first time); even 16 hours. This would serve as both an attempt of a fix and as a test.
If still "...shows not fully charged...", then either the battery even if new has faulted or the charger may have an issue.