Please be aware that invoices are sent by email only when you pay by BANK details.
If you pay your subscription by CREDIT CARD, you will not receive any emails unless an issue occurs when charging your credit card.
In any case, you can access the relevant Admin Portal to retrieve all your invoices:
|Cloudimage Admin Portal||Filerobot Admin Portal|
Account > Billing / Invoices > Invoices
Setting > Account > Invoices