[dcminter]

It does sound like there's something wrong with your CV and/or cover letter(s).

As others have said, "near 40" should not be putting you anywhere near age-discrimination issues, particularly at the CV-filtering stage.

Questions that occur to me: Are you applying to companies that are actively seeking? Are you applying to specific roles? If you are applying to specific roles is it obvious that your experience is applicable to those roles? Is your CV too long (over 4 sides, or less but a very small font) ? Is your CV too short (under a side) ?

Feel free to email me if you'd like me to give it a (confidential) once-over and provide any hot-takes on what the issue might be (am an ex-UK contractor with a few remote stints under my belt).

Edit: You could also ask a recruiter for feedback on your CV. They're experts (hopefully)) on selling candidates so it's worth asking.