Hello MikePS,
It sounds like you are following the recommended steps below: Use iCloud to share and collaborate on files and folders - Apple Support
Invite people to collaborate on files or folders
1. To invite people to collaborate on files or folders, do one of the following on your Mac:
• Click the Finder icon 
in the Dock to open a Finder window, click iCloud Drive in the sidebar, select a file or folder, then click the Share button 
.
• Control-click an item on the desktop, then choose Share from the shortcut menu.
Note: To collaborate with others on a file or folder, it must be in iCloud Drive.
2. Choose Collaborate from the pop-up menu.
3. Click “Only invited people can edit.” below Collaborate to set permissions for working together, then choose one of the following from the pop-up menu below “Who can access”:
• Only invited people: Allow only people you invite to access the file or folder.
• Anyone with the link: Allow anyone who receives the link to access the file or folder. If you choose this option, people you invite can share the link and give access to others not included in your original invitation.
4. Click the pop-up menu below Permissions, then choose one of the following:
• Can make changes: Allow people you invite to view and modify the contents of the file or folder.
• View only: Allow people you invite to view the contents of the file or folder, but not modify them.
5. Select the checkbox next to “Allow others to invite” to allow anyone with access to the file or folder to share it with others. Deselect the checkbox so only you can share the file or folder with others.
6. Share the invitation using Mail or Messages, or create and copy a link to the shared item.
Since you aren't seeing those options as expected, do you experience the same behavior when using the iCloud website per the steps below? Share files and folders in iCloud Drive on iCloud.com - Apple Support
Share files and folders
1. In iCloud Drive on iCloud.com, select the file or folder you want to share, then click 
.
2. Click Share Options, then choose who can access the file or folder, who can make changes, and if participants can add people to the file or folder.
3. Choose how you want to share the link:
• Email: Click Share. In the email window that appears, invite participants by adding their email addresses or phone numbers in the To field. Make any additional edits to the email, then click Send. The email option is only available when you have iCloud Mail turned on.
• Copy Link: After you select Copy Link, a text box appears. Add the email addresses or phone numbers of your participants. Click Share. A new window appears with the link for your file. Copy the link and send it.
When you share a folder, only the participants can view the files in the shared folder. To invite more people to access the files, you must change the settings of the shared folder. You can’t select an individual file or folder within the shared folder and add participants to it.
Let us know your result, and we'll keep moving forward from there.
