@sdetweil I found the solution,
thank you !
i had to install valid-url :

npm install valid-url

@sdetweil here is the errors it gives, but i’m not sure to understand…

0|mmstart  | [22.03.2021 18:32.13.033] [ERROR] WARNING! Could not load config file. Starting with default configuration. Error found: Error: Cannot find module 'valid-url'
0|mmstart  | [22.03.2021 18:32.13.084] [ERROR] Whoops! There was an uncaught exception...
0|mmstart  | [22.03.2021 18:32.13.139] [ERROR] { Error: Cannot find module 'valid-url'
0|mmstart  |     at Function.Module._resolveFilename (internal/modules/cjs/loader.js:636:15)
0|mmstart  |     at Function.Module._resolveFilename (/home/pi/MagicMirror/node_modules/module-alias/index.js:49:29)
0|mmstart  |     at Function.Module._load (internal/modules/cjs/loader.js:562:25)
0|mmstart  |     at Module.require (internal/modules/cjs/loader.js:690:17)
0|mmstart  |     at require (internal/modules/cjs/helpers.js:25:18)
0|mmstart  |     at Object.<anonymous> (/home/pi/MagicMirror/modules/MMM-CalendarExt2/node_helper.js:3:18)
0|mmstart  |     at Module._compile (internal/modules/cjs/loader.js:776:30)
0|mmstart  |     at Object.Module._extensions..js (internal/modules/cjs/loader.js:787:10)
0|mmstart  |     at Module.load (internal/modules/cjs/loader.js:653:32)
0|mmstart  |     at tryModuleLoad (internal/modules/cjs/loader.js:593:12) code: 'MODULE_NOT_FOUND' }
0|mmstart  | [22.03.2021 18:32.13.149] [ERROR] MagicMirror will not quit, but it might be a good idea to check why this happened. Maybe no internet connection?
0|mmstart  | [22.03.2021 18:32.13.159] [ERROR] If you think this really is an issue, please open an issue on GitHub: https://github.com/MichMich/MagicMirror/issues
0|mmstart  |
0|mmstart  |
0|mmstart  | X.Org X Server 1.20.4
0|mmstart  | X Protocol Version 11, Revision 0
0|mmstart  | Build Operating System: Linux 4.15.0-48-generic armv8l Raspbian
0|mmstart  | Current Operating System: Linux raspberrypi 4.19.97+ #1294 Thu Jan 30 13:10:54 GMT 2020 armv6l
0|mmstart  | Kernel command line: coherent_pool=1M 8250.nr_uarts=0 bcm2708_fb.fbwidth=1600 bcm2708_fb.fbheight=900 bcm2708_fb.fbswap=1 smsc95xx.macaddr=B8:27:EB:EA:17:C7 vc_mem.mem_base=0x1ec00000 vc_mem.mem_size=0x20000000  console=ttyS0,115200 console=tty1 root=PARTUUID=738a4d67-02 rootfstype=ext4 elevator=deadline fsck.repair=yes rootwait
0|mmstart  | Build Date: 05 June 2019  12:49:54PM
0|mmstart  | xorg-server 2:1.20.4-1+rpt1 (https://www.debian.org/support)
0|mmstart  | Current version of pixman: 0.36.0
0|mmstart  |    Before reporting problems, check http://wiki.x.org
0|mmstart  |    to make sure that you have the latest version.
0|mmstart  | Markers: (--) probed, (**) from config file, (==) default setting,
0|mmstart  |    (++) from command line, (!!) notice, (II) informational,
0|mmstart  |    (WW) warning, (EE) error, (NI) not implemented, (??) unknown.
0|mmstart  | (==) Log file: "/var/log/Xorg.0.log", Time: Mon Mar 22 18:32:36 2021
0|mmstart  | (==) Using system config directory "/usr/share/X11/xorg.conf.d"
0|mmstart  | [589:589:0322/183259.671712:ERROR:gl_implementation.cc(282)] Failed to load libGLESv2.so.2: libGLESv2.so.2: cannot open shared object file: No such file or directory
0|mmstart  | [589:589:0322/183259.829795:ERROR:viz_main_impl.cc(176)] Exiting GPU process due to errors during initialization
0|mmstart  | [547:893:0322/183307.059505:ERROR:object_proxy.cc(632)] Failed to call method: org.freedesktop.DBus.Properties.Get: object_path= /org/freedesktop/UPower: org.freedesktop.DBus.Error.ServiceUnknown: The name org.freedesktop.UPower was not provided by any .service files
0|mmstart  | [547:893:0322/183307.082801:ERROR:object_proxy.cc(632)] Failed to call method: org.freedesktop.UPower.GetDisplayDevice: object_path= /org/freedesktop/UPower: org.freedesktop.DBus.Error.ServiceUnknown: The name org.freedesktop.UPower was not provided by any .service files
0|mmstart  | [547:893:0322/183307.111738:ERROR:object_proxy.cc(632)] Failed to call method: org.freedesktop.UPower.EnumerateDevices: object_path= /org/freedesktop/UPower: org.freedesktop.DBus.Error.ServiceUnknown: The name org.freedesktop.UPower was not provided by any .service files
0|mmstart  | Fontconfig error: Cannot load default config file

@sdetweil thank you for the help !
it doesn’t work with this :
https://www.google.com/calendar/ical/ovb564thnod82u5c4njut98728%40group.calendar.google.com/public/basic.ics
this is the url in the example

hello, I can’t display my calendar, it works with the basic calendar but not with MMM-CalendarExt2, I used the code example, but magic mirror shows me “This site can’t be reached”, I have the same with MMM-CalendarExt.
For information, I work with a raspberry pi zero W.
Could someone help me please ?