did you e-file the amended return?
it is possible the employer never submitted the w-2 to the Social Security Adm. Employers are supposed to submit them to the SSA and then the SSA computers send the wage info to the IRS computers. try calling the employer but you may not get the right answer.
if you mailed the amended return did you include a copy of the W-2? if not I would resubmit the 1040-X with the w-2. the IRS is behind in processing paper returns so it could take 6 months or more before you hear anything from them. (or call to find out what to do, maybe you can fax them a copy). if you mail it use a method where you can get proof of delivery
one other thing to do is get a wage transcript from the IRS to see how that matches up with what you reported. you can get it online if you have already set up an account otherwise you'll have to do it.
https://sa.www4.irs.gov/secureaccess/ui/?TYPE=33554433&REALMOID=06-00008e4d-63f6-1187-a229-7c2b0ad00...
if that is what the IRS is missing from its records, you can try calling it at 800-829-1040
warning the iRS phone lines are often busy you may have to make many attempts
explain your situation, and ask the agent what you should do
First choose your language.
Then 2
Then 1
Then 3
Then 2
When asked for SSN do nothing it will ask twice
Then 2
Then 4
the IRS will need contact info for the employer and depending on what the employer does this could take some time
finally after maybe half a dozen attempts to get through to the IRS which fail you can try your states IRS Taxpayers Advocate
you can try contacting the IRS Tax Advoate in your state.
