The Rance tidal power station [1] in France has been operating since 1966 so I don't think that there are technical issues, at least with this type of tidal power generation (ie. a dam across a tidal estuary and good old turbines to produce electricity). That specific power station doubles as a much needed road bridge, as well.
It wouldn't be legal to build Rance in the EU today, because of the enormously disruptive effects on the local ecosystem. It's not something that bothers me personally, but it's a total dealbreaker in a country like the UK where wildlife activists hold considerably more political sway that climate activists.
There was a project to build a tidal lagoon in Cardiff [1] that was eventually abandoned, and I don't know about the environmental impact. But it had the merit of being ambitious.
It has been operating - but it was a research project and it's not like tidal has proliferated since then. Not quite a dead end yet - people are still working on submerged tidal kinds of things. But close.
[1] https://en.wikipedia.org/wiki/Rance_Tidal_Power_Station