Correo de limit and access to services has been restricted

I received the following email, what does it mean, because I didn’t understand anything?

Please note that your Sentinel Hub account has reached the monthly limits and access to services has been restricted.

Restrictions will be lifted at the beginning of next cycle. In case you need services beforehand, we recommend to purchase top-up processing units or upgrade your account.

If you have any queries, please don’t hesitate to contact our Support

This means that your consumption exceeded the freely available quota of your subscription package (see packages option, “Processing volume” section.
You are welcome to upgrade to a higher tier or purchase top-up processing units.

Do you have any links that you can give me for refills ? (purchase top-up processing units)

Sure, this one:
https://apps.sentinel-hub.com/dashboard/#/account/billing
Processing tab.

This option is available to users with Basic or Enterprise subscription.
I have exploration, there is no way to buy processing units with this plan ?

No, you will indeed have to upgrade to a higher tier.