fund account
It may be related to VAT (if the system indentified you for VAT so the price may be more than 30 for example) .
Anyway, you can ask the service desk about it:
for financial issues, please contact the Service Desk — Contacts and requests >> Create a request >> Finance >> Other question >> write your message — https://www.mql5.com/en/contact
Yes, as Sergey already mentioned, it is related to VAT, your $30 purchase has an extra $5.70 VAT added.
I have 30USD in my mql5 account, but cannot buy an indicator for 30USD, because I don't have enough funds ! Please sort this out.
Your 'automated robot' is probably the worst in the entire internet.