On Friday, out of the blue...no admin changes had been made, our page layouts went on the blink. All but six fields have disappeared on the page. When you go to edit, the full page layout shows up, but in preview you can only see the same six fields (out about 20). If you add or delete fields there are no changes in preview, although I can remove and add any one of the six fields. Starting a new page layout from scratch doesn't help either...only one of the six fields will show up when saved. Even stranger this impacts page layouts for Accounts, Contacts, etc. I can't find any one with this problem...any thoughts are greatly appreciated.
Since, when you edit the page layout all the related lists are available so here is the resolution to find the issues:
User's profile should have access to the object and related fields.
If user has access to the objects, even then he is not able to see the related list then only option is user may have removed the related list by his own way.
Basically, open the record detail page and find the
Customize Page link.
Then in the below page, assign the related list in selected list side. Be sure to assign in the proper order. Because, this ordering overwrites the ordering the page layouts during display.