Hi,
preview pages 234+ of the classroom learner handbook for early years educator level 3 (link is to amazon.co.uk) offers good reading about the barriers that might exist with partnership working. It doesn't list impossibles or state how these barriers are totally insurmountable rather it identifies the working hours or other commitments that parents could have that might prevent them from becoming as wholly involved with their child's setting as the setting may like.
Other areas are parent's own self esteem and self confidence, not feeling as though they have anything worthwhile or of value to contribute.
Dealing with attitudes often presents challenges as does discrimination. Professional training, skills, the ability to be supportive, find solutions, plus the funding to better this expertise can also present barriers to working effectively with parents.
Parenting styles and approaches to raising children may differ from what practitioner's know to be respectful of children's needs.
Priorities between the setting and parents might differ eg. the balance between spending quality time together and the anxiety or requirement felt to get children to sleep in the evenings or be toilet trained by a particular age may be tilted.
Gaining parental consent and permissions.
Knowledge about how to support children at home may not be as heightened as the information that's acquired and shared in a professional setting where practitioners are submersed in supporting children's care, learning, development and how best to do that eg. the value of books, time together, consistency and routines, all weather play.
The English language and communicating with parents who have an alternative first language or difficulty with reading and writing.
Recognising the information that each of us has, that another may not have is an important aspect of information-sharing. Knowing when to give, what to give and how to ask for information can cause problems.
Preschool parent notice board ideas - google image search
Research links:
The impact of parental involvement Charles Desforges 2003 on PEAL
Provider influence on the home learning environment 2011 on gov.uk
Early home learning matters practice guide funded by the 2009 Government Department for Children, Schools and Families and
Poverty & life chances report by Frank Fields MP
Onsite
activity ideas to support home-setting communications 
Hope this helps a little xx