I have quite literally just had this.
As a companies IT tech, I supplied an updated SSL cert, key etc to the "tech" people that maintain their AGFA software
Them "can we have this as a .cer and key"
Them "It doesnt work *pastes error from Firefox"
Me "send me the logs"
Them *sends a few lines of the log*
Me "The WHOLE log"
Them *sends log with first line being TomCat having a hissy fit over the key not matching"
Me "Check you are using the right key"
Them "We are *pastes error of Tomcat telling me they are lying"
*rince and repeat for 4 hours
In this time I've re-issued the cert, converted it to every format known to man AND used it on an internet facing apache box to verify its fine including screenshots of they key matching, chain of authority etc
Them "It still doesnt work"
Me "It does work, see above, theres alll the evidence"
Them "It doesnt work for us! It must be your certificate"
Me *points to evidence there IS no issue*
Me "Ok, try this..*issues free included SSL cert I'm not using from IONOS"
Them "that works"
Me "Ok, there's something weird with your setup, can you look into it and let me know what you find so we can dodge this next year"
Me "Found the issue, the version of Tomcat you are using is old (and needs to be taken round the back of the barn) and has some issues with RSA keys
Them "Oh we know about that, it'll be upgraded next year"
Me *Sends customer invoice for two days of out of contract consulting on a 5 minute job with a note *Blame Supplier"