Why could I not partake in Presybyterian communion?

[GenevieveRose]

Hello! Here’s my question: I have been raised in a strong and devout Catholic family, and although I understand that I will never stop learning about the Faith, it might be safe to call me at least an “educated” Catholic.
I have a friend who is an Orthodox Presbyterian. He invited me to attend his church’s Sunday service. Because he is my brother in Christ, and for reasons of future evangelization, I was happy to attend.
However, my mom told me that I could not share in the Presbyterian communion (which this community receives every week.)
I know that for them it is only a symbol, and since I was advised not to, I did not receive.
What is the reason why I could not partake of Protestant communion?
Thank you for answering this question!

 

[Fr.Charles_Grondin]

The very word communion implies a union of sorts and things in common. Unfortunately Christianity is divided and there are many things that we do not hold in common and we are not united. To receive communion implicitly states a fellowship of belief, thought, or action among those receiving. For a Catholic to receive communion in a nonCatholic community would essentially be a public lie since the act of receiving communion implies that we are in union with each other.
Another pitfall of receiving communion, especially in communities without a valid Eucharist, is that we can imply a sense of indifference to the importance of a true and valid Eucharist.