It is not uncommon to find iPhone having problems receiving Messages from Android phone users, while having no problems receiving messages from iPhone users. This usually happens, when iPhone is well connected to home or office Wi-Fi network; but it is going through cellular network connectivity issues.
In such cases, iPhone is able to receive iMessages from Apple device users (via Wi-Fi & iCloud), while being unable to receive SMS Text messages from Android device users.
iPhone Not Receiving Text Messages from Android Users
If your iPhone is not receiving text messages specifically from Android users, make sure that it is connected to cellular data. If the signal strength is weak or if the cellular data network of your service provider is going problems, you will have wait until the issue is resolved.
If the problem is not being caused due to cellular data connectivity issues, you can move to other steps as provided below in this guide.
1. Refresh Cellular Network
Since, the problem could be network related, start by enabling and disabling the Airplane mode on your iPhone.
1. Open Settings > enable Airplane Mode by moving the slider to ON position.

2. Wait for 30 seconds > disable Airplane Mode by moving the slider to OFF position.
2. Make Sure MMS Messaging is Enabled
You won’t be able to receive messages with attachments from Android device users, if MMS (Multi-Messaging Service) is not enabled on your device.
1. Go to Settings > Apps > Messages.
2. On Messages screen, scroll down to “Text Messaging” section and enable MMS Messaging.

After this your iPhone will be able to receive messages with photo and other attachments sent by Android device users.
3. Check Blocked Numbers
The problem might be due to the phone number of your Android contact being blocked on your iPhone.
1. Go to Settings > Apps > Messages > scroll down and tap on Blocked Contacts.
2. On the next screen, swipe left on the blocked Phone Number and select the Unblock option.

After this, you should have no problem receiving text messages from your Contact using Android phone.
4. Make Sure Phone Number Is Listed
While iPhone can receive iMessages using Apple ID from other Apple device users, it needs a phone number to receive SMS text messages sent by Android device users.
Hence, make sure that your phone number is listed and available for use by the Messages App on your iPhone.
1. Go to Settings > Apps > Messages > tap on Send & Receive.
2. On the next screen, make sure your Phone Number is listed and selected to receive Messages.

5. Temporarily Disable RCS on Android Phone
If you are having problems receiving a specific message from an Android device user, you can request your Android Contact to disable RCS and see if this helps in fixing the issue.
This can make the Android device to bypass RCS and send that particular message using the standard SMS/MMS protocol.
Note: Current versions of iOS (18 +plus onwards) should have no problem handling RCS.