This has been resolved. It turned out to be a long running query that had the entire database locked. It came to our attention from tech support monitoring the database. I wish I had known how to look for that myself.
Thank You for telling me how to find the %TEMP% but %TEMP%\!S.log was not in the directory.
And to answer your other question, I was able to create directories in other databases using the same protocol just not in the one where it was needed.
I appreciate the time you took to look into this.

No, that's not WinSCP log file.
To locate the %TEMP%, just paste it to Windows File Explorer address bar.
Also, you didn't really answer this question:
Can you create the directory using any other client using the same protocol?

Is this the log?

And this is the final message in the attachment.

Hi,

Here is more information.
I believe logging has been enabled. And the log file is here
%TEMP%\!S.log
but I don't know how to find where %TEMP% is.
Also I attached some screenshots but may have attached them more than one time. If so I apologize.

Hi, thank you for your reply.
FTP is the protocol.
WinSCP Version 5.17.7 (Build 10640).
Windows 10 Pro 20H2.
Yes I can create a directory using ftp on the production server but not on the development server. Two weeks ago the development server was at 100% capacity and the space was doubled. It has again filled to 100% capacity. I was advised to find and delete older, large files and I did that. It still showed 100% capacity. Then I cleared cache and still cannot add a directory. I didn't ask the person who told me it was at 100% to check again because it was giving the same error.
I think there must be some way to release the space that was occupied by the deleted files but do not know how to do that.
You suggested enabling logging but I am unable to figure out how to do that.
So, two questions.
How to enable logging.
How to release space that was occupied by the now-deleted files.
Thank You

What protocol are you using? Can you create the directory using any other client using the same protocol? Please attach a full session log file showing the problem (using the latest version of WinSCP).

I am trying to create a new directory and getting message "Create directory operation failed."
There is no information as to why it failed or how to correct it.
Does anyone have any suggestions?