Does the employer or insurance company have an obligation to provide advance notice that Group extended health benefits are no longer being provided?
I don’t think the Group extended health benefits insurance carrier would ever proactively communicate to you that your health benefits will no longer be provided. I think they will confirm “after the fact” that your coverage has been terminated if you actually phone them or sign in on-line to check the status of your benefits. If the employer is terminating Group extended health benefits for all employees, they would normally advise everyone in advance but the legal “obligation” for a non-union group would be an interesting question especially in these COVID days.
I think your employer would normally advise you in advance that they are terminating your Group extended health benefits even if you are on an approved LTD claim. Some employers terminate these benefits for employees on LTD, but that is less common than you may be lead to believe if you read the internet.
Are you sure that your Group Health Benefits are no longer being provided? It could be we are just early in 2021 and your deductible has not yet been reached (often the first $25, $50 or $100 is not paid).
Not to alarm you, but it is possible that your LTD has been terminated. Of course, your LTD provider would communicate this to you in advance, but with COVID it is always possible that things fall through the cracks. When your LTD is terminated, the insurance company that administers your LTD claim communicates your termination to your employer. Only people on an approved LTD claim or approved leave are eligible to remain on the employer’s Group extended health benefits plan. If you’ve actually been terminated from your LTD claim, you should contact your employer to let them know you are still sick (assuming you are) and provide whatever information they require in order that you might remain eligible for your employer’s Group extended health benefits plan (even if you need to pay the premium).
If memory serves Jammer has a type of disability that doesn’t go away so no concerns about LTD being terminated. 
In my province at least the employer would have to give prior notice on similar terms to giving notice of termination because it’s a material change to your terms of employment. Is it possible that they switched to a different carrier and your HR department forgot to warn the people who were out on leave?
I meant if the employer terminates your employment for “frustration of contract” and by extension your benefits go away.
This is hypothetical.
I wondered if the employer or insurance company has to notify you.
I have a permanent physical disability so I don’t worry much about LTD being terminated.
If an employee has been on an approved LTD claim and they are still “employed” (eg. still has extended health benefits) after 6 years then is the chance of being fired (frustration of contract) less than the first 4 years?
Probably depends more on what is going on with the business and who is in management. If they are selling the company or having to lay off staff they might revisit the status of people who are on leave.