[galaxy-user] Galaxy error: can't fine fasta file

Hello, I'm new to Galaxy. When I read in a fasta file to Galaxy and then try to use it (in a blast search) as the query sequence, I get the error message below, although the uploaded fasta file is present in the history. Can anyone tell me what the problem could be? Is there some other step I need to do? Thank you. Error that appears under "nucleotide query sequence": ----- "History does not include a dataset of the required format / build" -----