Hey there, welcome to the Community!
I've had a quick look through most of the add-ons/powerups that provide Gantt functionality:
On the surface I didn't find any of these solutions mentioning they were shutting down. Is there a particular one of these you know you happen to use (or another solution entirely)? I'd be happy to look into a specific powerup for you if you know which one you're currently using.
Ah, thanks for confirming. I can't find any shutdown notices for Trellogantt anywhere, but given that their website is now offline and you're receiving that message in-product, I think it's safe to assume the service will no longer work.
I'd recommend taking a look at the list of alternatives above. There are several to choose from.
If you had to thrive a new habit during a lockdown, what would it be? Trello
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