One day, I was driving down the street and saw a panel truck with “Maranatha Plumbing” painted on the side. “Maranatha” is an Aramaic phrase (the Jewish people in Jesus’ days spoke Aramaic, the language of the Babylonian Captivity). It probably means “Our Lord, Come!” which would be appropriate for a plumber racing to fix a bathroom emergency; however, I think the man was trying to indicate he was a Christian plumber and so answered to a higher standard.
Even the early Greek-speaking Christians used many Aramaic words such as “amen” and “Abba” (Father). Jesus himself spoke Aramaic (see Matthew 27:46 and Mark 5:41). The phrase “Maranatha” or more appropriately, “marana tha” or “maran atha” was used by the first Christians (See 1 Corinthians 16:22 and Revelation 22:20).
Because Maranatha is simply transliterated from Aramaic into Greek, it isn’t easy to know exactly how to translate it into English. It could be māran(ā’)’ aṯā’, “our Lord has come,” or māran(ā’) (’ ĕ)ṯā’, “our Lord, come!” What difference does it make?
The Didache is an early Christian church manual. It gave instructions about baptism, worship, and church practices. We have many books like that available today that provide suggested talks for weddings, funerals, and speaking at the Lord’s Table. The Didache suggests:
But let no one eat or drink of your Eucharist except those who have been baptized into the name of the Lord, for the Lord has also spoken concerning this: “Do not give what is holy to dogs.”
And after you have had enough, give thanks as follows:
(2) We give you thanks, Holy Father,
for your holy name, which you
have caused to dwell in our hearts,
and for the knowledge and faith and immortality
which you have made known to us
through Jesus your servant;
to you be the glory forever.
(3) You, almighty Master, created all things for your name’s sake,
and gave food and drink to men to enjoy,
that they might give you thanks;
but to us, you have graciously given
spiritual food and drink,
and eternal life through your servant.
(4) Above all, we give thanks because you are mighty;
to you be the glory forever.
(5) Remember your church, Lord,
to deliver it from all evil
and to make it perfect in your love;
and gather it, the one that has been sanctified,
from the four winds into your kingdom,
which you have prepared for it;
for yours is the power and the glory forever.
(6) May grace come, and may this world pass away.
Hosanna to the God of David.
If anyone is holy, let him come;
if anyone is not, let him repent.
Notice how the suggested prayer ends with two Aramaic words: “Maranatha!” And “Amen.” In this case, it makes good sense to translate Maranatha as “the Lord has come!” and that’s why we can enjoy the communion.
On the other hand, Paul’s conclusion to First Corinthians and the exclamation in Revelation probably mean, “Come! Lord.”
Both translations are blessings: “The Lord has come!” (Hallelujah!) and “Come back soon!”
 Holmes, M. W. (1999). The Apostolic Fathers: Greek texts and English translations (Updated ed., pp. 261–263). Baker Books.