Hi @Pauline Johnson ,
I'm glad to hear you solve the problem, if you have any issue about SharePoint, you are welcome to raise a ticket in this forum.
By the way, since the Microsoft Q&A community has a policy that "The question author cannot accept their own answer. They can only accept answers by others.". and according to the scenario introduced here: Answering your own questions on Microsoft Q&A, I would make a brief summary of this thread:
Issue Symptom:
Request failed unexpected response data from server. null::
When accessing the site content page I am getting this kind of error. Please see it in Screenshot. after I click on ok, I am getting the normal page "Site Content".
Unexpected response from server. The status code of response is 400. The status text of response is ::
We are able to successfully created the document library but unable to create the folder in the library.
500 Internal server error
Unable to upload the new document or download the document or any other file from site content, we are getting the 500 internal server error, Please find the screenshot.
Current status:
I have run the SharePoint product Configuration Wizard on all Servers, and the issue got resolved.
The configuration wizard running process takes around 45 min on each server, Claims windows token service restarted multiplied times.
You could click the "Accept Answer" button for this summary to close this thread, and this can make it easier for other community member's to see the useful information when reading this thread. Thanks for your understanding!
If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.