When you receive a WordPress Image upload error nothing is more annoying. If you’re just having problems with a single picture, start by looking at the file’s name. If you use special characters such as #, @, %, & or accent letters (, á, é), the WordPress uploader may have problems. It’s also possible that the picture is too big, both in regards to dimensions and file size. The size of a picture must be changed. https://www.wordpresssupport.co/image-upload-issue-in-wordpress/
To fix this, you need to increase the amount of memory PHP can use on your server. You can do this by adding the following code to your wp-config. php file.