I have been running an application on a MKR 1010 Wifi for the past 5 years with no issues. The application is supposed to connect to smtp.gmail.com:465 to send email every 12 hours.
I had uploaded the SSL Root Certificates at the time of commissioning the application:
As I said, this has been working perfectly and continuously for the past 5 years.
Last week, I had a 5 day Internet outage. The incoming fiber optics cable had been damaged.
So for those 5 days, the application tried and failed to send email.
Then, when Internet was re-established, the application could no longer connect to smtp.gmail.com:465.
After some debugging, I used the Arduino IDE to upload again the same SSL Root Certificates and all was well again.
Could anyone offer an explanation as to how the previously uploaded certificates could stop working as a result of a 5 day outage, and 5 days of failed connection attempts?
I speculate that your MKR lost time and date, and when that happens certificates usually no longer works. This means that it wasn't the reupload of the certificate but when the MKR got time synced that solved the problem.
This is not entirely true, if your using the Arduino MKR Wifi 1010 with the Bear SSL library and the built in certificates then i do believe there is some time tracking implementation built into that library as i have had some issues connecting to AWS IOT core using these devices and was getting a time related error.
Thanks for your reply, but again, I am not using BEAR SSL, only loading SSL Root certificates to the board via the IDE as per these instructions.
In my understanding there is no way to modify the uploaded root certificates once they are on the board.
On the other hand, I could not establish an SSL connevtion to the google smtp server until I re-loaded the root certificates...
The only thing that had happened in between working and not working was loads of attempted connections when there was no Internet available over my wifi network...