English Translation
I have been silent for a long time.
Replace {{ごぶさた}} with {{ご無沙汰}} in Kanji. We usually prefer Kanji for ご無沙汰. Also, the default TTS as well as Google Translate TTS pronounce the whole sentence with {{ごぶさた}} in a very natural way…
GT can pronounce 長いことご無沙汰しました。properly.
ご無沙汰 consists of ご (prefix for polite expressions) + 無 (non-) + 沙汰.
沙汰 (さた) means “a final decision or judgment” or “notifying such a decision/judgment to others”. 無沙汰をする as a compound verb means “not keep you updated (on my recent status)”.
長いことご無沙汰してます or しました has a connotation of “apologize for” not keeping you updated for such a long time.