I am receiving benefits from LTD currently. 8 am 62. My insurer indicates that I have to apply for CPP Disability..that this is mandatory. Is this the case?
I was approved for LTD Oct, 2022.

Under a lot of (if not most) LTD policies, you do have a duty to apply for CPPD benefits. The insurer puts that in there because they get a deduction for anything you receive (or could have received had you applied) from CPPD.

To be sure that this applies to you though, you could ask your case manager at the insurance company to send you the policy section that they're relying on in claiming that you have a duty to apply.