I've found a work around - open your microsoft windows calendar (click on the time/date in the bottom left hand corner) and link your yahoo calendar into the microsoft calendar - seems to work OK so far! Good luck!
So I've sent some info you asked for but not sure how useful it will be as the PM system is nowhere near as sophisticated for the type of details required. I've also left a contact point should you wish to contact me directly asw speaking is way easier than this system seems to be. good luck and please feel free to let me know if its any help.
To others on here I've repeated my answers to Johns questions as it may be useful for others - if not sorry for wasting peoples time.
Both myself and my wife are getting the same issue on separate desktop PC machines.
The exact affected account email address
<censored>@btinternet.com (Mywife does not use the calendar part but its same issue with her when I checked it.)
The exact steps you are following that leads up to the issue occurring
Open bt.com (in a browser chrome, firefox etc)
Select email from Menu option
Login to BT/Yahoo email using bt email address and P/W
Once email opens in the either the latest or older email environment
Select the calendar icon 2nd from left in the right hand side to the left of the New email Settings options
Once selected the calendar screen will appear using (https://calendar.yahoo.com/) url.
A detailed description of the exact issue being seen
See attached pictures below for my emails systems (I've removed them for security).
The exact date and time (with time zone) of the most recent attempt or replication of the issue
2nd September 2019 14:02 (Uk time zone).
The exact text of any error message being seen
No error messages but some items seem like they work. (My view is that anyone logging in with a BT/Yahoo email will get this error) I never went further for fear of making a mistake and deleting my current alerts.
The exact version of supported web browsers in use (Internet Explorer not supported)
Chrome Version 76.0.3809.100 (Official Build) (64-bit)
Firefox version 68.0.2 (64-bit)
Vivaldi 1.15.1147.64 (Stable channel) (32-bit)
All on a desktop in my case running windows 7 - but I'm sure many who are running windows 10 etc will have the same Issues. I have tried all these but my normal browser would be the Chrome. That was updated last week but this has been happening for quite some time across number of version updates.
Any other details you feel would be helpful with the investigation
Whilst I've supplied all the above I believe with hand on heart anyone having a BT/Yahoo account and trying to use the webcalendar will have an issue with a web browser on a desktop. As I said in a recent message there may be a correlation to the url everyone will be receiving as not being a correct routing URL. That said I have not inspected the code to see what is happening at a browser level to see whether the code is passing parameters to the url we are receiving.
This whole issue has been going on for some considerable time and usually its solved after a few days by itself but in this instance it has not resolved in the last week or more which I guess is resulting in the annoyance.
The mangled calendar screen does have some functionality but I have always refrained from using it as it always seemed that it was not correct and was too concerned that my existing alerts might be inadvertently be corrupted or worse deleted in error.
<images removed for security reasons - roughly translated means I didn't have time to edit bits out.>
Lucky old Windows 10 users, I'm guessing us poor boys on Windows 7 don't seem to have that option but I'm happy to be corrected.
One satisfied customer anyway! 😁 Until MS decide to remove the app from W10 who knows they can barely deliver an update that doesn't shut down 1000's of peoples machines in the last few updates if the computer press is anything to go by.
Further to my earlier post; I did get a call from some dubious sounding (Indian?) girl claiming to be from BT but it was vary vague and she sounded confused (I actually thought it was one of those scamming calls where they try to take control of your PC/device to rob your data), but before we could make any sense of anything she hung up.
Apart from that, no return call. I will now rasie a complaint.
Re. question as to the link to Yahoo mail that has a working calendar, just Google Yahoo mail login. You need to log out of BT mail first and you need a email@example.com/.com email address.
Re. Linking BT mail claendar to microsoft calendar, how do we do this? I opened my Windows 10 Pro calendar (selecting clock at bottom right of screen) but couldn't see any option to link to any other calendar. Suggestions please?
JohnC2; Any update or progress?
Update: no progress, I have now formally raised a complaint 2 days ago so lets see where this takes us !? No progress so far other than to say they are investigating.