The jump signs don't work

"Please tell me how you could do that."

The first thing I did was notice, as Jojo says, you have two DCs. One is a DC al Coda and the other just a straight DC. I assumed you wanted the DC al Coda as you have a coda and so I deleted the one that was just a DC. Then i looked at the "cross hairs" Coda sign attached to bar 8. I have seen scores where this sort of sign is used to mean "jump from here to a similar sign at the coda". But within Musescore this is only used as the "landing point" for a jump to coda. For a jump to Coda to work you have to have a "To Coda" as the "jump from point". However, the text associated with the "To Coda" (as with any jump) can be edited and I assumed you wanted the notation to be as I described above "jump from here to a similar sign at the coda". I deleted the "cross hairs" Coda sign in bar 8 and dragged a "To Coda" from the Repeats and Jumps palette. Then I edited the text of the "To Coda" by replacing the text with a "cross hairs" Coda sign from the symbols palette. I adjusted the font size to match the real Coda sign at bar 18.

Then I played it through and found that the DC al Coda that remained after I deleted the DC didn't work. I am not sure why but I guessed that MuseScore had ignored the DC al Coda when it was entered as there was already a DC and that just deleting the superfluous DC did not re-create the correct playback sequence. So I deleted the DC al Coda and added it again in the same place. Then everything worked as I expected.

The whole thing took about 5 minutes, including the test playthroughs.

I must say that as a player I would prefer an explicit "To Coda" rather than the matching "cross hairs" version, but I thought you might be trying to reproduce an existing score that uses that notation and so did the text editing trick.