ios – Mutual authentication between my iPhone and webserver

I need to be able to access a secure portion of my website from my iPhone.
It’s a site directory (“infra”) where I keep information and routines to manage my home’s infrastructure UPS and comms status.
I have implemented it using mutual authentication, on each client (browser) that needs to get and put data I have a client certificate (infra_client.cer) which has been issued by my private ca. This works fine on normal desktop browsers but not on safari or chrome on my iPhone, despite the fact that the client certificate and the ca certificate are loaded settings/general/profiles and appear to be verified.
When I try to connect the server says:

(Mon Jul 12 06:44:02.452293 2021) (ssl:error) (pid 10010) SSL Library Error: error:140890C7:SSL routines:ssl3_get_client_certificate:peer did not return a certificate -- No CAs known to server for verification?
(Mon Jul 12 06:44:02.599346 2021) (ssl:error) (pid 10059) (client AH02261: Re-negotiation handshake failed

has anybody any ideas how this can be made to work?