@VictorKHanson-0152 Apologies for the delay in response.
You can activate up to 4 sandbox environments per day. Once you have used all your sandboxes for the day, you'll need to wait 24 hours before you can activate additional sandboxes.
You can refer to this doc for more information.
Can you please confirm if you had already used the quota of 4 for the day for which you are getting this error or using the 3 sandbox itself is throwing the error?