I got this particular issue termed "Description contains illegal characters" when I was trying to set up a gig, and I wasn't able to save my description, let alone progress to the next section (requirements). I had to come over to the Fiverr forum to seek help on finding the solution to the issue, of which I was later able to gather quality information and precautions on how I can easily go about it, which I will also like to share with you (the newbies) in here on some practices that are not ideal when writing a Fiverr gig description:
1)Don't copy and paste content Directly: If you paste content from a program like Word into the gig description box, it may contain tab characters or other character codes that Fiverr will not allow.
The document should work if the non-visible or non-standard ASCII characters are removed before pasting it into the gig description box on Fiverr.
It could be possible to save it in a standard text file format using Notepad (by pasting it there) and then possibly reopen the regular text file format version of it before putting it into Fiverr's box.
However, Below are also things you need to put in likewise take note, if you wish to have a successful gig that convert
Making false or exaggerated claims: You should avoid making claims that are not true or are exaggerated just to make your gig look more attractive.
Using poor grammar and spelling: It is important to make sure that your gig description is free of spelling and grammar errors, as this will make your description look unprofessional.
Including irrelevant information: You should only include information that is relevant to your gig, as including irrelevant information will only confuse potential buyers.
Not being clear and concise: Your gig description should be clear and concise, so that potential buyers can easily understand what you are offering.