Some DNS service providers require you to split long TXT resource records into 255 characters parts.
The most notable DNS service provider requiring manual splitting is Google Cloud DNS, which gives you a cryptic 'invalid record data' error if you don't split the input. We even devoted a blog post on the subject.
This 255 character restriction is usually encountered with DKIM records, as those are often longer than 255 characters.
You can use this tool to split a DNS resource record value into 255 character parts. Just paste the record here and the result will appear below.