Welcome to the WPML support forum. I will do my best to help you to resolve the issue.
We had a similar issue in the past. But it was using fixer.io API for Automatic Exchange Rates. Please check the following ticket for more details. Which plan you are using for currencylayer?
The CURL 28 error means that your server was unable to communicate to the currencylayer within the set time limit. This can be caused by, for example, a slow Internet, WebHost, or firewall settings.
Please visit WooCommerce>>WooCommerce Mulitiligual>>Multicurrency tab or Products in frontend in secondary currency. Then make sure the issue is existing or not.
I believe it could come from the following message:
message: You have exceeded your daily/monthly API rate limit. Please review and upgrade your subscription plan at hidden link to continue. (oktober 15, 2022 1:36 pm)
I have changed the update frequency from hourly to daily. Let's see if that solves the problem.
This ticket is now closed. If you're a WPML client and need related help, please open a new support ticket.