found lost phone

hi i found my i phone 13 pro max after around 7 to 8 months is there any other way now i can activate my this lost phone . but now on this phone is message is comin THERE IS A PROBLEM WITH YOUR IPHONE. THIS IPHONE CANNOT BE ACTIVATED FOR SERVICE.PLEACE CONTACT YOUR NETWORK PROVIDER OR APPLECARE.can you please let me know now what i have to do know to activate this iphone.

thanks in advance