Error in match(x, table, nomatch = 0L) : 'match' requires vector arguments

I am trying to do some Bioconductor exercises on R studio cloud. Running the first two codes (#1,#2) have been fine, but the last code(#3) gives the error message. Please can anyone help?

#1 Transcribe dna_seq into an RNAString object and print it
 dna_seq <- subseq(unlist(zikaVirus), end = 21)
 dna_seq
  21-letter "DNAString" instance
seq: AGTTGTTGATCTGTGTGAGTC



#2 Transcribe dna_seq into an RNAString object and print it
 rna_seq <- RNAString(dna_seq) 
 rna_seq
  21-letter "RNAString" instance
seq: AGUUGUUGAUCUGUGUGAGUC

#3 Translate rna_seq into an AAString object and print it
aa_seq <- translate(rna_seq)
aa_seq

 aa_seq <- translate(rna_seq)

Error in match(x, table, nomatch = 0L) : 'match' requires vector arguments aa_seq Error: object 'aa_seq' not found