Incorrect file format and corrupted data

[Resrchintl]

I am having a significant level of loading failures in 2025 with "Incorrect file format, file should be from PTC Mathcad Prime" and "File contains corrupted data" errors as the causes:.  23 cases are appended. What is most concerning is that projects that have been used to launch improved models a few days earlier as well as intentional project copies, both cannot be opened then or a few months later.   Is anyone else seeing an increase?  The "incorrect file format" is a new error for me.  It looks like it may be necessary to store PDF copies of projects, as some of these programs are 50-100 pages in length and will take days to weeks to reconstitute. Two .mcdx programs I tried to upload were rejected as having as having an incorrect file extension..  Is there something wrong with the title "250525, Tac7C+Weatherstation, corrected firmware, threaded slab heater, slope analysis.mcdx" ?

[LucMeekes]

1. The 'incorrect file format' error occurs frequently, especially with Prime sheet files that are large due to embedded pictures.

Prime has a habit of corrupting such worksheet files upon saving too often, but some users shut down their machines too soon, while a sheet file is still being saved. Saving files on a network, or in the cloud could also be a potential cause of trouble.

2. This forum uses software that checks the type of file being uploaded. For some reason it rejects certain files that Prime is happy to open. (Forum 'thinks' it is smarter than Prime...?)

3. The only potentially offending character in the file name "250525, Tac7C+Weatherstation, corrected firmware, threaded slab heater, slope analysis.mcdx" could be the "+", you might try to use an ampersand "&" instead.

4. Your attached worksheet file is corrupt. It still may contain a lot of information, but probably contains some pictures. The FIXED file attached here should open in your Prime 10, but without any pictures.

Success!

Luc

[Resrchintl]

The file comes up perfectly now, and by the way, I NEVER put photos in mathcad files- that was a hard lesson learned a couple of years ago!  Thank you very much.  The program that would not load was developed over a two month period   and there is probably a man-week of effort in that document. I tried attaching it to this response as a ".zip" in the hope that you could do the same magic to it, but that is not an allowed uploadable either.  It appears to upload with a ".dat" extension.    Virtually all the unreadable files in 2025 were backups made prior to embarking on significant project changes- perhaps I need to wait longer before going at the renamed file again?  Is there anything a user can  do personally to claw back after this kind of crash? 

[LucMeekes · Accepted solution]

I wonder what happened to get the file so corrupted. The .dat file was 13 MB, the fixed .mcdx is now 104 kB...

I hope this is all that's supposed to be in the file.

Success!
Luc

[Resrchintl]

It works fine now.  Thank you so much.  The program was in part processing a weather file that was about 20,000 lines x 38 columns in size, and the saved program is again around 12MB instead of 100KB.  Oddly, as a separate issue it appeared the input data had lost its '.csv' extension and was gibberish.  That fortunately was easy to reload from raw data.  Whew!