Download of full BLAST hits from protein BLAST against the PDB database is not currently possible due to a configuration change at NCBI.
It is still possible to get protein BLAST summaries ('Matching region'), but retrieving the 'Full sequence with annotations' from the BLAST options will fail with the error shown below, and so will downloading the full sequence from summary documents.
Blasting against and downloading hits from a nucleotide database is not affected by this change and continues to work as usual. This also does not affect protein BLAST searches against the UniProtKB/Swiss-Prot database.
We are currently investigating the cause of this issue and hope to have it resolved as soon as possible. We apologize for any inconvenience this causes in the meantime.