I disabled data for WhatsApp on 1st April (as a substitute to uninstall). Now I have turned it 'ON' back, on 10th May, and I received messages from the month of May only. Didn't receive any message from the month of April. It may look like that no one messaged me in April but it's not true. I have been part of highly active groups, and in the groups too, there's been no message for the month of April. How can I retrieve those April messages?
However, if you disabled WhatsApp data on the 1st of April, you off stopped being able to receive any of these messages when they were first sent. If these messages were sent again today, you should receive them as you have turned data back on.
In these group chats, could you see messages appearing throughout April? If you never saw any messages, then you probably won't be able to retrieve them.