"I was no longer working for X" vs. "I no longer worked for X"

I'm a student learning English and recently helped a friend of mine write an important email in English. The text I gave him contained the following part:

I am sorry for not replying to your email, but I was no longer working for X and did not regularly check my email box at X. When I saw and read your email, I supposed you did not need my advice anymore, as a considerable amount of time had elapsed. I apologize for not replying.

(Here X substitutes the name of the company my friend had left.)

The friend changed "was no longer working" to "no longer worked," saying I had made an obvious error, and I'm pondering as to whether he is right.

On the one hand, I've been taught that the main criterion to choose between the simple tense and the continuous tense is whether the sentence is about a regular action or, on the contrary, about someone being in the very process of doing something. This criterion seems to indicate that my friend is right. He left the company a couple of weeks before the email seeking his advice landed in his email box at that company.

But, on the other hand, I chose the continuous tense in that sentence instinctively, and I know from experience that my quick intuitive choices are usually correct. Perhaps I had seen similar phrases in books or articles. I've read a lot of them, and this really helps me write my own texts. I didn't even think as to which tense to choose - I expressed the idea as my subconscious mind dictated it. Curious, I've just typed the exact phrase "was no longer working for" in Google and got really many search results. Furthermore, I've just recalled reading an article about a message all residents of New Zealand received from their government in relation to the coronavirus, and that message contained the following sentence:

You must only be in physical contact with those you are living with.

Here the continuous tense is chosen, just like in my original text.

My question: Whose variant is better and why?

Solution 1:

There is a mismatch of tenses, which is bad style. Since working and check are parallel verbs in the sentence, and there is no semantic reason to put them in different tenses, they should be in the same tense. So your friend was correct in that something was wrong with the sentence, but it's not clear that he identified the correct "obvious error".

You should either say

I was no longer working for X and was not regularly checking my email box at X,

or

I no longer worked for X and did not regularly check my email box at X.

I slightly prefer the continuous tense, but both options are grammatical, and both sound fine to me.