Can an ex-spouse get Military Retirement after the divorce decree is final?

Depends on the language in the Final Judgment. Have the document reviewed by an attorney ASAP. Sometimes DFAS takes the position a spouse has only one year to apply for some benefits.

What was agreed to in the divorce? You didn't say. If there was no disposition of that issue, it usually cannot be revisited.

Generally, a spouse's share in any military benefits is determined and awarded during the divorce, not after. There can be circumstances under which your branch of service may still award a spousal share of benefits, such as when the divorce judgment is silent on the issue. You should consult with a family law attorney with experience in military divorces to discuss your specific situation and your options.