Clearing cache via URL doesn’t work

Hello, I’m trying to clear all cache via URL in Plesk. I made a cronjob as described on https://www.wpfastestcache.com/features/clear-cache-via-url/
I’ve also set this line of code in wp-config.php: define(‘WPFC_CLEAR_CACHE_URL_TOKEN’, ‘123abc’);

When I start the cron job in Plesk, I get the following error message:
Die Aufgabe “https://www.mydomain.com/? action=wpfastestcache&type=clearcache&token=123abc” wurde in 0 Sekunden abgeschlossen, jedoch traten Fehler auf
curl: (3) URL using bad/illegal format or missing URL
Unable to fetch URL: https://www.mydomain.com/? action=wpfastestcache&type=clearcache&token=123abc

Why isn’t it working? Thanks in advance for your help!
Andreas