Yes, you need to revalidate if you received a notice and have been assigned a revalidation due date.
In accordance with Section 6401 (a) of the Patient Protection and Affordable Care Act, all new and existing providers must be reevaluated under the new screening guidelines. Medicare requires all enrolled providers and suppliers to revalidate their enrollment information every five years (reference 42 CFR Section 424.515). To ensure compliance with these requirements, existing regulations at CFR 42 Section 424.515(d) provide that the CMS is permitted to conduct off-cycle revalidations for certain program integrity purposes.
Read the article: How to Search on the Medicare Revalidation List Tool for Due Date to look up if the enrollment has a due date.