Almost every writer has suffered from writer's block and there are no sure cures for the condition. A writer writes. That's the sum total of the problem and may be the solution. I've suffered three times in my career from being unable to write. Maybe the causes were unique to me but they may be reasons other people can relate to.
One - A meeting with an agent who liked my writing. She asked me to bring three ideas when I traveled to NYC for a meeting with her. I wrote three sketches of books I thought she might see the value of. She read them and then told me, "They're good. Just pick one and write the book." That's when it hit me. Those weren't my stories. They were ones I thought someone else would like. The ideas were good but really not my kind of books.
Two - Had an editor like a book and she made detailed suggestions on a book that was essentially written. Her suggestions were great. Now comes the kicker. Making the suggested changes set me off on a different direction and a different story. For several weeks I tried to fit the changes into the book I'd written and mostly sat and stared at the pages. Because of the suggested changes I saw a different book and not the one I'd already written. The suggestions were wonderful but not for the book I'd written. A new book was all I could see.
Three - Having written three novellas that are interconnected, I need a fourth to complete the series. For the past six months I have toyed with this concept and nothing came to mind. I jotted down scenarios that sounded reasonable but I was unable to write more than a paragraph or two. Just the other day something started bubbling in my unconscious. It's not ready yet, but I think I will be able to finish the quartet.
Now for the bit of advice. Writer's block can be caused by writing something that's so not you, having changes suggested that don't fit your story and by being unable to find the proper vehicle for a story. Are there cures? Perhaps but each person must find his or her own. Mine is this Be true to yourself and write what you'd like to read.