Can we amend our tax return to add AOTC now? When I originally filed I received a message saying it was "not available, and to check back later in the year".

yes you can amend.  the return must  be mailed.  use a method where you can track it. 

 

 

https://ttlc.intuit.com/questions/1894381-how-to-amend-change-or-correct-a-return-you-already-filed?jump_to=answer_3288565

 

A 1040X cannot be e-filed.  It must be printed and mailed.  It will take about 3-4 months for the IRS to process an amended return.  It is a good idea to use a mailing service that will track it, like UPS or certified mail, so you will know it was received.

Wait about 3 weeks from mailing and you can check the status of your amended return:

https://www.irs.gov/Filing/Individuals/Amended-Returns-(Form-1040-X)/Wheres-My-Amended-Return-1

https://www.irs.gov/filing/individuals/amended-returns-form-1040-x/amended-return-frequently-asked-questions

https://ttlc.intuit.com/questions/1908543-do-i-need-to-amend

 

https://ttlc.intuit.com/questions/2566895-what-does-it-mean-to-amend-a-return