Return delayed question

My tax return was e filed and it has been well over a month. I called the irs and they told me that I was getting a cpo5 notice that it is under review for either income or tax credit verification. I did have a baby this year so it is my first year filing for a child tax credit and filed head of household when I normally do single, (her father recently changed his address to my house and does make more money than me however I do provide more for the household as we split rent and I am the one buying groceries, baby items, household items etc..he pays for the cars and car insurance which isn’t household related) but what I think the REAL problem is if anyone can give me any insight is that my employer didn’t file my w2. Would that cause the delay? I left the company at the beginning of the year and I was the one handling my payroll and filing the companies state unemployment, sales & use, and payroll taxes. Since I left, it just dawned on me that nobody is probably there to do the taxes. I printed my W2 out when I left so that’s how I had it but they say they didn’t do their portion of it by sending anything in on their part because I used to do it when I worked there. I’m thinking this is why they need to verify my income, because I included my daughter social on the return so I don’t know what they would have to verify as far as the tax credit. Do you think this is what the problem is? My employer needs to file my w2 with the IRS and that’s why they need to verify my income? The notice does not tell me much this is all I could think of.