Q: What does it mean if I have not received a reply from the editor for 40 days after submitting my revised manuscript?

40 days is a bit long since submitting a revised manuscript and not hearing anything from the editor. It may be that either the editor or the peer reviewer/s is/are busy. If the latter is the case, the editor is probably waiting for the respective peer reviewer to get free, as it’s best to have the revised manuscript reviewed by the same reviewer.

Anyhow, again, 40 days is quite a bit to not hear from the journal (though you may have at least seen an auto-status message since then). So, you can write to the editor requesting an update on the revision. In case you need help with the email, you may refer to this handbook of email templates by R Upskill, a family brand providing a range of learning courses for researchers/academics: How To Communicate With The Journal? This particular handbook includes templates for a variety of communication scenarios, including asking about a delay in the decision. So, do check it out.

Hope you hear from them soon. All the best for all the next steps on your manuscript!