The online help is fairly straightforward when talking about Ties: “The two notes must be the same pitch but can be in different voices or on different staves belonging to the same instrument”
However in the example below, I am unable to tie the Eb down stem note to the Eb in the next measure.
Are you explicitly selecting both notes, not just selecting the first and pressing T?
I clicked on the first note and pressed T. Then I tried using the tie button. It didn’t tie. Oh, I also tried clicking on both notes and it didn’t work either.
Selecting both notes explicitly (ie clicking one then Ctrl/Cmd-clicking the other) then inputting the tie should work provided they are the same pitch and belong to the same instrument, as described on this page.
If that’s reliably not happening in a project, please do share it.
Also, maybe it’s just me but your images are coming up basically entirely white, I could only see black stave lines and notes for the 2nd picture when I expanded it.
I saw the image problem but you replied so quickly that I didn’t have time to swap out the images. Not sure what happened there. I’ll try and replace the images.
Apparently we have an intermittent bug. I did select both notes as described and then pressed T. Nothing happened. I went to some things in my DAW. Just now I loaded Dorico again and tried it and it worked. I know I’m not going senile, I really did click on both notes and press T. I don’t know. Sorry to bother everyone.
I doubt it. This feature has been reliable for many people for a long time.
Are you absolutely certain both pitches are/were E-flat? Try using “show accidental” to make sure.
It could be that switching between apps and windows meant the key command wasn’t functioning, but the toolbox button would have. If you encounter it again, share the project and reproduction steps for someone to investigate.
For some reason I’m not able to set this tie (l.v. in the example). Both are e.
Well, I’m not surprised, since it would be rhythmically flawed. Try changing the first note as an 8th note, it should work 
If you insist on this notation, use a 2:1e hidden tuplet.
Thanks, Marc. It is in the original score like that. I don’t see why this is rhythmically flawed. The first e1 is a quarter:
The hidden tuplet did the trick 
Dorico won’t tie together notes that overlap rhythmically. They can at most abut, but they cannot overlap.
…I think Marc and Daniel are saying it is rhythmically flawed to tie; it is not rhythmically flawed per se. As Marc said making the first e an eighth should solve it - or maybe add an e eighth in the second voice and tie that.
I have opted for the version with the hidden tuplet, as suggested by Marc. There is an autograph and two prints of this piece. All three sources note it like this:
In the autograph from 1854 it looks like this:
@Juerg_Loeffler, I’m not a great fan of the rests that some editors add to such places in keyboard music, but in this case, I 'd be tempted to add a quarter rest a the beginning of the measure in the alto parts; perhaps in brackets.
Yes, @John_Ruggero, I was also tempted to add the rest in the alto part, but then thought that the quarter rest in the left hand makes it unquestionable that the c1/e1 of the right hand comes on beat 2.
I’d have thought the earlier debate about why Dorico won’t notate it without hidden tuplets might tell you that the RH is ambiguous.
Personally I think it’s OK to correct original MS errors (with an editorial note). My suggestion for the RH would be:
Missing rests in parts are quite normal in romantic piano music. I can’t imagine that a pianist would play this passage incorrectly due to a lack of clarity. Strictly speaking, the alto part has no e1 on the second quaver.
@Juerg_Loeffler Normally I would agree that the left hand rest and positioning of the alto and tenor voices directly over each other should suffice… But in this case, the potential confusion has to do with the rather tight spacing in both the original and your engraving, which places the tied Es quite close together, so that it begins to resemble normal offsetting of unison note heads in neighboring parts. And the natural sign makes it resemble places where the offsetting has to be a little greater than usual because of an accidental has to be interposed.