If you have the error, do not just start clicking randomly. Follow this protocol to isolate the issue.
: Look for files with .sbk or .ed.backup extensions.
If you want, I can:
The error typically occurs when STAAD.Pro cannot recognize the basic structure or header of your .std input file. Primary Fixes
Once you have recovered your model, implement these five best practices. This Is Not A Valid Staad Command File
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If the file is severely corrupted, use the auto-generated backup files. ServiceNow This is not a Valid STAAD Command file... - Communities If you have the error, do not just start clicking randomly
If you meant this as an actual user error message you saw, let me know and I can help you debug the actual .std file instead.