MKR board package not working

Just loaded the latest MKR 1400 board package and now I get this error when I try to complile:

Arduino: 1.8.8 (Windows Store 1.8.19.0) (Windows 10), Board: "Arduino MKR GSM 1400"

In file included from C:\Users\alan\Documents\ArduinoData\packages\arduino\tools\CMSIS-Atmel\1.1.0/CMSIS/Device/ATMEL/samd21/include/samd21.h:69:0,

                 from C:\Users\alan\Documents\ArduinoData\packages\arduino\tools\CMSIS-Atmel\1.1.0/CMSIS/Device/ATMEL/samd.h:105,

                 from C:\Users\alan\Documents\ArduinoData\packages\arduino\tools\CMSIS-Atmel\1.1.0/CMSIS/Device/ATMEL/sam.h:470,

                 from C:\Users\alan\Documents\ArduinoData\packages\arduino\hardware\samd\1.6.20\cores\arduino/Arduino.h:48,

                 from sketch\sketch_dec14a.ino.cpp:1:

C:\Users\alan\Documents\ArduinoData\packages\arduino\tools\CMSIS-Atmel\1.1.0/CMSIS/Device/ATMEL/samd21/include/samd21g18a.h:237:26: fatal error: core_cm0plus.h: No such file or directory

 #include <core_cm0plus.h>

                          ^

compilation terminated.

exit status 1
Error compiling for board Arduino MKR GSM 1400.

This report would have more information with
"Show verbose output during compilation"
option enabled in File -> Preferences.

I've tried reinstalling the IDE (Windows store) and removing the board package and reinstalling it but that didn't help. Any suggestions?

I just tried another computer, downloaded the new board package for the MKR 1400 1.6.20 and now I get the following:

Arduino: 1.8.8 (Windows Store 1.8.19.0) (Windows 10), Board: "Arduino MKR GSM 1400"

RVMonitor:3:20: error: MKRGSM.h: No such file or directory

 #include <MKRGSM.h>

                    ^

compilation terminated.

exit status 1
MKRGSM.h: No such file or directory

This report would have more information with
"Show verbose output during compilation"
option enabled in File -> Preferences.

Any help would be appreciated - hope the world is not coming to an end!

There was a report here of an antivirus software causing the error:
https://forum.arduino.cc/index.php?topic=526899
That's not the cause I would have expected, but it's worth a try to see if the problem goes away after you temporarily disable your antivirus. If so, you will need make the appropriate changes to your antivirus's whitelist settings so that it doesn't interfere with the compilation process.

Thanks, but that didn't seem to help on the first computer. On the second computer, I simply forgot to download MKRGSM, so that installation is fine. I still need help on solving the first issue.

Thanks.

I reinstalled a third time and now everything works fine.