It sounds to me that you have entered two notes of the same pitch and are attempting to tie them together so that only one note plays. If you have entered two notes, both will play. Try deleting the second note and changing the length of the first note to take up the additional note length where the second note was.

Samples below show with a Slur added (which doesn't work), and an automatic Tie is added by lengthening the single note (which does work):

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2023-01-22_14-24-33.jpg (47.91 KB, 45 downloads)
2023-01-22_14-26-50.jpg (54.74 KB, 44 downloads)

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