You can still file a married filing jointly, (MFJ) tax return if your husband is not required to file a tax return. That way you will get to claim your husband as an exemption and have a more favorable tax rate along with enhanced deductions and credits compared to filing married filing separately, (MFS).
When you file MFS, you can only claim yourself and not your husband, that is why you are getting that message. So my advice would be to go back and choose MFJ. You will pay a lot less in taxes by doing so.