Just began seeing this error in the automation log a few days ago:
Error encountered in step with name [Sent to I-Car Cal]: The conversion could not be completed because the supplied DateTime did not have the Kind property set correctly. For example, when the Kind property is DateTimeKind.Local, the source time zone must be TimeZoneInfo.Local. (Parameter ‘sourceTimeZone’)
Emails with ICS attachments are now failing to be delivered. Nothing has changed with the app or template. Ideas?
If anyone else is having ICS calendar invitations fail in email automations in a similar fashion, Appsheet support has had to escalate this because they can’t figure it out, either. Appears to be a possible bug in Appsheet. I encourage you to file a support ticket if you have the same issue.
THANK YOU! I am having the same issue and will open a support ticket.
Patrick_Paul…were you able to get your issue resolved?
Yes, I’m experiencing the same issue with a feature that was previously working perfectly. The ability to send calendar invites is a crucial part of our app’s functionality and it’s essential for our operations.
Appsheet support is saying the problem is caused by my key value being set to a time stamp value…but that doesn’t really make sense to me. The rest of my bot is running just fine…the problem seems to occur with the .ics file. I am looking into rewriting the task with appscript as a work around. Please reply if you find a fix!
I am experiencing the same issue as well. I’ll open a support ticket.
Hi @Patrick_Paul I have raised a support ticket, but have not heard anything at all from the AppSheet support team, only the usual acknowledgement. Have you heard anything further, or know of a possible work around?
I got an answer from them saying the problem was caused by the fact that my key field was a timestamp value. In that true in your application?
Hi @anita_frasier no, my calendar entries are recorded in a Log table, where the Key is LogUUID, which VarChar. Clearly there is a timestamp element because it is recording a meeting event with a start time, end time and end date.
Did their suggestion resolve your issue? 
No, I chatted with support initially and they tried a few things to no avail, then escalated it. The day after, I got the usual notification that someone with Appsheet was accessing my app for support purposes, after that, nothing.
Fortunately this doesn’t render the whole app useless, but it is causing a problem.
Chat rep had me try changing the field from a date to a datetime and that had no effect on the problem, FYI.
I was just setting up a test environment when you replied! It just doesn’t sound right to me…and sounds less right now that you’re saying that your key is not a timestamp value!!
@Harriswe …the answer is No - changing the key in a development copy of the app had no impact. Back to support…
Thank you for the update @Patrick_Paul .
I’ve had to work around this issue by disabling the functionality that generated the ICS file, which had been working fine and just sending an email instead. It seems there are several AppSheet errors recently affecting functionalities that haven’t changed for a while.
Unfortunately, the response time for solutions has slowed down compared to what it used to be.
I encountered a synchronization error that essentially rendered one of the apps unusable for anyone not running the stable version. Even worse, it incorrectly reported that the stable version was also impacted, making a rollback impossible and preventing users from switching to the stable version.
Google is still investigating this issue and it’s been ongoing since June. 
Sorry to read that @anita_frasier but not totally unexpected. ?
My ticket has now been escalated, too. Did this problem start for you guys on 7/9?
I believe I found my problem. My code creates all day events. The DTStart and DTEnd values in the .ics file were set to a value of “Value=Date;20240726T050000Z” Removing the time portion of the value (ie “Value=Date;20240726”) has corrected the issue in a test copy of my application. No changes were made to the app…so not sure why it suddenly stopped working. Hoping to update the production app on Monday or Tuesday. Hope this helps you guys!
This is it. Appsheet has still never gotten back to me on the ticket, but this is the source of the problem. My best guess would be that Google or someone changed how the ICS files are generated and somebody was left out of the loop.
Unfortunately, it doesn’t solve my issue as there are no time values in my DTStart and DTEnd. They take the date from the table so it is DTStart=<<[Date]>> and DTEnd=<<[Date]>>. It follows the same syntax from the Space Booking template I used to create the app. Just today, I even created a new test app using the same template and the same error is produced. There was definitely a change in how ICS files are generated as my app was working for without issue for months.
I went back to support with my findings and they are looking into it further.