I don’t have the option to invite others on my iPhone calendar

Good day to you djflaksdjflksdjflskadkjflsd, 

Could you please clarify for us, are you attempting to share a calendar or add invitees to an event? 

If you’re sending an invite to an even, are these the steps you’re following? Send invitations in Calendar on iPhone

Invite others to an event

You can invite people to an event you’ve scheduled.

1. Tap the event, then tap Edit near the top of the screen.

2. Tap Invitees.

3. Enter the names or email addresses of people you want to invite, or tap the plus sign to select Contacts.

Note: For you to send a calendar invitation to a contact, they must have an email address. See Add and use contact information on iPhone.

4. Tap Done.

If you don’t want to be notified when someone declines a meeting, go to Settings > Calendar, then turn off Show Invitee Declines.

Note: With Microsoft Exchange and some other exchange servers, you can invite people to an event even if you’re not the one who scheduled it.

When you view an event that you want to add someone to, or you’re looking at the calendar you want to share, is it an event or calendar that is syncing with whichever account you sync with? That might be iCloud or another service. 

Thanks. 

Greetings djflaksdjflksdjflskadkjflsd,

Thank you for confirming those details. Since there can be several calendars within the Calendar application, let's see if the issue continues if you create an event in a different calendar using the steps listed below.

1. Open the Calendar app.
2. Tap Calendars towards the bottom- center of the screen.
3. Tap add Calendar and create a test calendar for iCloud.
4. Once created, try creating an event for that calendar.

Let us know how that goes!

djflaksdjflksdjflskadkjflsd,

Thanks for getting back to us. To make sure, these are calendar events that you have scheduled, correct? Let's next try quitting the Calendar app, restarting the iPhone and then trying again. Restarting apps and the iPhone can reinitialize apps and settings.

Close an app on your iPhone or iPod touch - Apple Support

Restart your iPhone - Apple Support

Let us know how it goes.

Cheers.

Hi djflaksdjflksdjflskadkjflsd,

Thanks for testing with a different calendar. To have the issue investigated further, please reach out to support here: Apple Support

Best regards.