I think that "問題ない" isn't proper to answer for "フォローありがとうございます。" Here are some examples for it. どういたしまして。 ≒ No problem. / Not at all. / You are welcome. いえいえ ≒ No problem. / Not at all. またフォローしますね、 ≒ I goona click a like/recommend button on your blog/video site. or etc, again. わたしでよければ、いつでも。 ≒ I'll help you anytime if you like. "よかったです。" ≒ I'm glad for you. ”いつも応援してます。” ≒ I’ll always support you. / I'm always cheering for you. I think that these phrases + emoticons or face marks( (^^),(^o^),(^_^),(^^)/, etc.) make it more friendly. Here is a site of some examples for replying to "ありがとう". https://hikkirabo.com/%E3%80%8C%E3%81%82%E3%82%8A%E3%81%8C%E3%81%A8%E3%81%86%E3%81%94%E3%81%96%E3%81%84%E3%81%BE%E3%81%99%E3%80%82%E3%80%8D%E3%80%8C%E3%81%82%E3%82%8A%E3%81%8C%E3%81%A8%E3%81%86%E3%81%94%E3%81%96%E3%81%84/