Why doesn't my iphone 15 recieve group messages and messages from android?

For sending to SMS group message and SMS to Andoid devices...

You need to have an SMS/MMS plan enabled by your carrier for the SIM/eSIM that you use on your device. Apple Inc. does not provide SMS/MMS services.

Types of group text messages

There are three types of group messages that you might see: group iMessage, group MMS, and group SMS. The Messages app automatically chooses the type of group message to send based on settings, network connection, and carrier plan. For example:

• If you and your recipients are using Apple devices and iMessage is turned on, then the group message is sent as an iMessage.
• If you send a group message to people who aren't using iMessage, then the message is sent as an MMS or SMS message.