OK. Are you using Companion 2.58 or not?
You " made numerous changes on the designer screen since my last connection over AI companion". Did you create a series of aia files of the Project as you progressed? If you did make the backup files or Save project as and saved previous versions you could use the aia or other versions if you get tired and mess up. If you have a back up, you could back out to a usable version if needed.
What happens if you load a back up file of your penultimate aia?
Yes on the 2.58.
Unfortunately, no saving different files along the way.
What I can’t understand is that if I completely delete everything in the designer,that it still does not work.
Could you export the bad project to an .aia file and post that here for analysis?
Loaded it up, deleted everything, and it still generated the error message on refresh when connected to companion (this on a linux system with genymotion emulator). Odd.
MicroSplit_empty.aia (1.1 KB)
Hello,
I have the same problem and i fix it.
1.export the bad project
2 create a copy
3. rename your bad project to a *.zip and open the zip, open src/appinventor… to the end. you have 2 files, if you have one screen (Screen1.scm and Screen1.bky) extract Screen1.scm and open it with notepad++
4. there is a line code in the beginning like that :
{“authURL”:[“ai2.appinventor.mit.edu”],“YaVersion”:“205”,“Source”:“Form”,“Properties”:{"$Name":“Screen1”,"$Type":“Form”,"$Version":“27”,“AppName”:“PlaniF”,“Column”:“3”,“PrimaryColor”:"&HFF000000",“Row”:“0”,“Scrollable”:“True”,“ShowListsAsJson”:“False”,“Title”:“PlaniF”,“Uuid”:“0”,“VersionName”:“1.01”,"$Components"…
5. remove “Column”:“3” and “Row”:“0” with ,
6 save the file, replace it on your *.zip
7 rename your *.zip to a *.aia
8 import your project.
that’s all
Only Column:0 in the original aia 
you can make ti with the copy if you want
Just tested by removing Column:0 and Row:0 from the scm file, and it seems to have solved it. Well done @Svetlana_GREGOIRE
So the question is, how did Column and Row get into Screen1 attributes?
Must have been put there by some component. Other question is, if that component was removed, why didn’t it take the column and row with it !! ? 
You guys rock.
Thank you very much!!!
hi i tried to do but i couldn’t I would be glad if you help
See also here for a simplified solution:
We have released nb183c, which will remove the errant Column and Row properties from Screens if they are present.