Excel cannot open this file message

I have a multipage workbook that I have been adding to and using daily for the last 6 months. Today my computer froze and I had to hold the power key down to shut it off. When I went to go back into the file, it couldn't find the file. I selected the file from the Open-Recent off the list the same way I do everytime I get into that file. I then went into Finder and looked for the file. The file name now showed a ~ in front of the name. I went into Get Info on the file and changed the name back. The extension correctly showed xlxs. I exited out of Finder and tried the open-resent again. This time it said: "The file format or file extension is not valid. Verify that the file has not been corrupted and that the file extension matches the format of the file." I have done everything that was on a different type of post possible including permission utility and I can't get this very important, non-replaceable file open. Unfortunately I've been in the process of selling my house/moving for the last 4 months and haven't done a backup since February. Since February is where most of my changes have been, of course. I am currently trying the Stellar Phoenix Mac Data recovery because of someone's previous post on another discussion. However after taking a long time to scan using the free software, it will not repair or do anything without paying for it. I was hoping to try one file before shelling out $100 since another poster said it didn't work and was a waste of money. Any help would be greatly appreciated. I'm almost beside myself because this file is so important and can't be recreated since it was gathered information over the last 4 months. 😟 One more thing. I tried to restore the file from February. My current file had at least 6-7 tabs, multiple equations from multiple tabs. The February file has one page of a little information. When I look at the Finder, the current file is 2 KB. The February file is 33 kb. I've obviously lost some information. HELP!