Exception Value: None (line 0) #68

Quando tento transmitir uma nota, recebo esse erro.

Exception Type: | XMLSyntaxError
Exception Value: | None (line 0)

lxml.py in fromstring
(linha 143) rootelement = _etree.fromstring(text, parser, base_url=base_url)

forbid_dtd = False
forbid_entities = True
parser = <lxml.etree.XMLParser object at 0x7fece098f550>
base_url = None
text = ''