Why does Military married to immigrants not receive stimulus check?

It depends.

If you are an active member of the U.S. Armed Forces only one spouse needs to have a valid Social Security Number to receive the stimulus payment.

If you did not receive your stimulus payment but met the requirements above, when you file your return in 2020, you will have the opportunity to report the amount of the stimulus check(s) you did receive, and if it was less than what you were entitled to, you will receive a credit on your tax return.

The payment of the stimulus funds can be tracked at the following website:

Check status of economic payment

Please see the following for facts related to the payments as processed by the IRS.  

FAQ for Economic payments

here are the qualifications that were part of the CARES Act.   

this is from the IRS FAQs 

A1.  You may be eligible to receive a Payment if you:

• Are a U.S. citizen or U.S. resident alien;
• Cannot be claimed as a dependent on someone else’s return;
• Have a Social Security number (SSN) that is valid for employment (valid SSN); and
• Exception: If either spouse is a member of the U.S. Armed Forces at any time during the taxable year, then only one spouse needs to have a valid SSN
• Have adjusted gross income below an amount based on your filing status and the number of your qualifying children.