Not sure when you e-filed your 2018 return---or when you think you e-filed it. E-filing has been permanently closed for 2018 returns since October of 2019. After that, the only way to file a 2018 return has been to print, sign and mail it in. If you tried to e-file it before the deadline last year, maybe it was rejected and you did not notice. If so, you can still file it but it has to be mailed.
Were you supposed to get a refund or do you owe tax due? Post back with more information on what you did to file 2018 so we know how to help you.