Hi, I’m sorry to hear you’re running into this issue. I may need to have you fill out the Pro Support Request Form with your System Report so I can investigate further.
One thing you may want to try though is setting up the
R34ICSPRO_INSTANCE constant in your wp-config.php file. See the section under Using a load balancer (e.g. Cloudflare)? on the ICS Calendar → Settings page in your site admin.