SendGrid Random HTML Comment Response

问题:

Have been trying to create a campaign with SendGrid API. Adding lists, recipients, and recipients to lists all works fine. However, as soon as I try to add a new campaign my curl response is:

<!-- This is a random-length HTML comment: jbxzwrreejuenlcislnnrtqpepguufquskweywdclekzbirxeqwozopyiewqhjumbhfwyepoosmzwyazpdzexczablujrbjiixmmmqjsashcfuwhguidzmnlqwpkmqkyqiuwbrdbiikvyyfkdxzfkcfvhsiqhpwowvtgvydjfabodxkdoycmhxhwhrqznppcaxevndlmftpomkoivcbkeonofgabbwalstlrajpptuhfdananzdgzlnavbinpxyzrgknkrqhyywwdnyhvgmwkvrcvheadfgdqvfviqdnrniqzfijxchyecjyzleznlwbfdlfbuwrbzlkaeftbhsiyoluymrzohgqxesvxxiadcpucmufdhcoenyeoagnssktmphhaximhfegozmayralqxdbbjfcoxxgeoqjsnbgyejalqmmpesmepqnbwykjaaorvljcxttkasnqxbkvrsshwkzywazfltmiyqdzugoezoaeynbkfsldmliqyiujnnriwgzendfgllnhyhxisimqojpncarhhhcyfxecwentpymluxvakpffuednakvxtplgclyjgprpyvwabkqldocwehynpucpgjukycrbsflglqljjitquqxnghesizdofkdvnzmxdrfopjqtvqvzffndalnaupeclmldvgoabignoeccpkbemyjyjeumyxzefrysrbtwpbdrhnkomvlnsrwctxwzioafmmovkybzpanychdfuvxovsnkuxchzmnuogngdcnuvaxuaejfwh -->

Which isn't even JSON. It worked earlier, and on previous days, but all of a sudden the API responses are making no sense.