WhatsApp texts not received until I open the app, regardless of notifications being on or off. Senders see a single gray check until I manually enter the app. Please help.

Hello Community,

After the last IOS update, I cannot receive WhatsApp messages on my IPhone 12 pro until I manually open the app.

Prior to the update, everyone on my contact list has been able to successfully send me messages and receive two gray checks, indicating that their messages have been delivered successfully.

For years, they have receive the two gray check marks whether I am in the app or not. Whether I have notifications on or not.

At present, all of my contacts receive a single gray check until I am physically in the app.

My carrier is ATT and recently I have upgraded to unlimited data for this account. Is there something I am missing? Is there a default setting for limiting cellular data consumption that turns on after a certain amount of usage?

Could that be what is happening that is creating this issue? Thank you for your steer.