Cannot edit/cannot return to v4

I switched to v3 this morning while building a form because v4 wouldn't allow me to edit a text field.  Now v3 isn't letting me add a field at all.  When I try to return to v4, the box goes away before I can click on it.  Any suggestions?  I've included the form link below

I have cloned your form but I was not able to replicate any of your issues. 

I was able to edit text field in Version 3 and in Version 4. 

In version 3 to edit text field, select your field and click on Edit HTML button. Then edit your text and click on Complete button.

In version 4 click on edit text option.

I was also able to add new fields in both versions. 

You can switch back to Version 4 on settings page of your account. 

I have cleared your form cache. Please try to edit your form again. You can also try to use some other browser. 

Let us know if you need further assistance.