deemer76 on "Keeps asking members to login again when using menu items"

I installed this on WP 4.5 to make the entire site private. Once the member logs in, things seem normal until they click on a different menu item to go to a different page on the website...why does this happen/how can I fix this?
Also, when they go from page to page, after a few clicks, a "429 - Too many requests" error keeps popping up.
I need a resolve asap ... many thanks in advance!

https://wordpress.org/plugins/members/