The company says that so many people are currently using the phrase – amid protests across the US – that it has automatically triggered anti-spam technology that has hidden the posts.
Instagram said that it was working to resolve the issue, as well as another problem keeping people from posting stories.
The new problems come as Instagram owner Facebook struggles to deal with the fallout from the protests that have swept the US. Mark Zuckerberg has been criticised by staff for failing to remove inflammatory posts from Donald Trump, in which he called protesters “THUGS” and suggested they could be shot.
The issues have been ongoing since at least the end of last week, with multiple users reporting that they were unable to post about the protests or related issues.
Instagram’s “action blocked” warning gives no context on why the post has been stopped, leading to yet more concern. It informs users only that the company “restricts certain content and actions to protect our community”.
In a series of tweets, Instagram recognised the problem and said it was working to fix it.
“We’re aware that some people are incorrectly running into “action blocked” messages when using the hashtag #blacklivesmatter, or resharing related posts. We have technology that detects rapidly increasing activity on Instagram to help combat spam,” its PR team wrote.
“Given the increase in content shared to #blacklivesmatter, this technology is incorrectly coming into effect. We are resolving this issue as quickly as we can, and investigating a separate issue uploading Stories.
“We want to be clear that using #blacklivesmatter is supported and celebrated on Instagram, and we are moving quickly to ensure voices using this hashtag are heard.”