email to kindle no longer sending series

[mytrivo]

A long time ago, I set up the metadata plugboard to add the series to mobi files emailed to my kindle. As of Jan. 13, 2020, this is no long happening. On Jan. 11, I emailed a mobi file to kindle and the series is there. But that's the last one it worked for. I've tried updating calibre, reentering the plugboard formula and I've looked through all the calibre preferences. I can't figure out what's going wrong.

Here is my metadata plugboard formula:
format -- mobi
device -- KINDLE2
source template -- {title}{series:| (|}{series_index:0>5.2f| #|)}
destination field -- title
the file name should to look like this -- Book Title (Series Name #01.00)
The files go through but only the Book Title appears on my Kindle Voyage and on my Amazon content docs page. I'm using a GMX email address, in case that makes any difference.

Any ideas or suggestions?

[stumped]

does it work if you sideload via USB. testing that may help narrow things down. both routes shoudl use same plugboard

[kovidgoyal]

Most likely you are emailling joint MOBIs. Metadata update will not work for them, so plugboards wont work for them either.

[mytrivo]

Originally Posted by kovidgoyal

Most likely you are emailling joint MOBIs. Metadata update will not work for them, so plugboards wont work for them either.

Under convert to mobi, in the mobi output section I have mobi file type set to old. Is there some other setting that needs to be checked?

Originally Posted by stumped

does it work if you sideload via USB. testing that may help narrow things down. both routes shoudl use same plugboard

I tried sending to device and yes it did include the series. I've never used this method before since emailing is so much easier. I guess I'll probably have to start doing it this way if I want the series info so show. It just seems strange that the email method used to work but now it doesn't. I really don't remember changing any settings anywhere in calibre.

[kovidgoyal]

No, old is fine.