With a number of online platforms many solutions offer different configuration setups or limits. Gsuite has DNS limitation for text record entries. There is a default of limitation 256 character for Gsuite when having to add a txt record.
This can be corrected by simply cascading the txt record especially when having to add ProofPoint Essentials DKIM record to Gsuite. The below screen screen shot will show you how the txt string looks before and after being cascaded.
v=DKIM1; k=rsa; t=s; n=core; p=MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAxuhaiEOlO+55mVa/9MFyqa/c2aV/w7VwMSZ9InN3Dg1JUYu3nMiuuKIDDahf4nAilMEZeMbp5IW9LEt6svflfZC9eP7aCTp+EDpSLH1aPVlI0zFgIhiecgjHwF58qn7BH4SRxG3Fn9oozaXrfHSFfn3NzmP9nlNOOWckY5pc26kYccJiWbKPDCZputpADxwqokBROVat3xOPg1JqC5pdCAhP6MKrjE1fz3MpIRHo2CJLFn1rMkPkxKhxoXA2YxJhfmt8V7wLQnbj/0Lcdxq7korcWtfJZNOWd+n4O6RKvARA4EzhLCdx/GjH/QUUCgdzMt9Rx5Ax5NJnLN38dGTrkwIDAQAB
"v=DKIM1; k=rsa; t=s; n=core; p=MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAxuhaiEOlO+55mVa/9MFyqa/c2aV/w7VwMSZ9InN3Dg1JUYu3nMiuuKIDDahf4nAilMEZeMbp5IW9LEt6svflfZC9eP7aCTp+EDpSLH1aPVlI0zFg" "IhiecgjHwF58qn7BH4SRxG3Fn9oozaXrfHSFfn3NzmP9nlNOOWckY5pc26kYccJiWbKPDCZputpADxwqokBROVat3xOPg1JqC5pdCAhP6MKrjE1fz3MpIRHo2CJLFn1rMkPkxKhxoXA2YxJhfmt8V7wLQnbj/0Lcdxq7korcWtfJZNOWd+n4O6RKvARA4EzhLCdx/GjH/QUUCgdzMt9Rx5Ax5NJnLN38dGTrkwIDAQAB"
If you have noticed the text record has not been split with the value of quotes assigned from the beginning of the string to about half the string followed by a closed quote. Then with a space, a third quote is added to being the second string and close off the text record with a final quote as well.