Play store not working and error while retrieving information from ser

I have a very old Samsung Tablet GT-P7300 tablet. It stopped working at one stage and then i reset it to factory settings. But the play store just does no work I then downloaded an older version of the playstore and the playstore works now but anytime that I try to download an app it gives a an error: "..." cant be downloaded. Try again and if the problem continues, get.help.troubleshooting. (Error while retrieving information from server[RPC:S-7:AEC-7 A7FS-VURI-P617G]). I just don't now what to do. I havetried to reset it to factory setting numerous times but the problem persists. I don't use my tablet for much I just use it for the kindle app so I use it as an e-reader. I do not want to buy a new tablet cause it is not worth it for me because of is use. Please can someone give me suggestions? Thnks