Sorry, there was a problem with "XXXXXXXXX". For support, please contact the developer

Sorry, there was a problem with "XXXXXXXXXX". For support, please contact the developer

When you are trying to add your app part to host web, then you will get this error.
Root Cause: You are missing   <WebPartPages:AllowFraming ID="AllowFraming" runat="server" />

Solution:

Add below tag in your app part pages.All the pages which you are using in app.
  <WebPartPages:AllowFraming ID="AllowFraming" runat="server" />

<asp:Content ContentPlaceHolderID="PlaceHolderMain" runat="server">
<WebPartPages:AllowFraming ID="AllowFraming" runat="server" />
<div>
Your code
</div>
</asp:Content>

Sorry, something went wrong

Sorry, something went wrong
No item exists at https://MySPO/teams/MySite/Style Library/MyPage.aspx. It may have been deleted or renamed by another user.

Root Cause: There might be lot of reasons for this error..
My error is related to "Edit Item Form" of a List.
I have added one edit item form in webpart page (MyPage.aspx), when i preview the page. I got above error.
Solution:
"Edit Item Form" will expect ID of the list item.
So you need to pass ID as query string.
Try this..
https://MySPO/teams/MySite/Style Library/MyPage.aspx?ID=10
Problem solved

Sorry, this site hasn't been shared with you in SharePoint 2013

Sorry, this site hasn't been shared with you in SharePoint 2013

Reason: You don't have access on SharePoint site.
Solution: Login to sharePoint site using administrator or user who is having access.
Click on Sharebutton.
Enter User name.
Click on SHow options, select full control.
Click Share.

Sorry, this site hasn’t been shared with you

Today i have got above error while accessing SharePoint 2013 Site Collection…

Fist i will explain the back ground what i have done..

From SP 2013 i have create a site collection using farm admin account.

I have added site collection administrator and secondary site collection admin as 2 names (No one is farm admin..)

Now i tried to access New site collection using farm admin.

hmmm…..i got above error message..

My Analysis: In SP 2013 security has trimmed , mean it’s more robust. Even though farm admin has created the site collection he will not be able to access the site collection directly. unless his name adds in to site collection, he will not able to get access .

In SharePoint 2010, farm admin used to access any site collection, even though his name is not added to Site Collection…

Solution:

Now i added farm admin name to site collection and able to access site collection…

problem solved…