Pop-up doesn't show? This may be triggered by "pop up block" setting on your browser.
Here's how you can enable the invite:
(Below guide based on Version 75.0.3770.142)
1. Select [Settings]
2. Click [Advanced] at the bottom to expand the options
3. Under [Privacy and security], click the [Site settings] button
4. At [Pop-ups and redirects], add Plair website to allow pop-up invite
If this problem continues, please report to us at firstname.lastname@example.org