The file is empty, incomplete or invalid
Check that the attachment finished downloading and is not zero bytes. Save it again from PEC or email and try the viewer again.
The .p7m name does not guarantee a valid CAdES envelope. Do not rename another format to make it appear to be P7M. If the problem remains, ask the sender to check the original.
The signature is detached from the document
A detached signature, often ending in .p7s, may not include the signed document. The viewer reports missing contents: the original document is needed alongside the signature.
Ask the sender for the document and use a validator supporting that signature type, or request an envelope with embedded contents. Renaming the signature does not add the missing document.
The envelope opens but the PDF does not display
A password-protected or damaged PDF may prevent previewing even when the P7M envelope is readable. If contents were extracted, choose “Download original” and open them in a suitable application.
This tool does not remove passwords or repair damaged documents. Request a new original if the file is incomplete.
The file exceeds 50 MB or browser memory is limited
The limit is 50 MB per file. Complex PDFs and long invoices can require additional memory even below that limit. Try an up-to-date browser on a computer with more available memory.
Do not cut or modify a signed envelope to reduce its size. Use a tool supporting the document if it exceeds this limit.
The XML is not a recognized invoice
Generic XML appears as text. This does not mean the P7M failed to open. PDF export is available for recognized FatturaPA invoices, not every XML file.
Malformed XML, DTD declarations and external entities are not supported. Contents are not executed as code and missing data is not invented.
The signature is invalid or not verified
Invalid integrity needs attention to the original file. “Not verified” may also mean a check is unsupported; it does not automatically mean a document was changed.
Read the signature details to see which checks were performed. Trust, revocation and timestamps need a dedicated validator.