timpttwtvfpnwtslemtweynuisyatatwihbaiwlts 

It simply means "I miss you". It's derived from the lyrics of Taylor Swift's Enchanted:

This is me praying that
This was the very first page
Not where the story line ends
My thoughts will echo your name, until I see you again
These are the words I held back, as I was leaving too soon.

Person A: I miss you...
Person B: timpttwtvfpnwtslemtweynuisyatatwihbaiwlts
Person A: 💜

timpttwtvfpnwtslemtweynuisyatatwihbaiwlts by All_too_bad(Taylor's Version) March 30, 2023

timpttwtvfpnwtslemtweynuisyatatwihbaiwlts 

It is an acronym of the lyrics of Taylor Swift's song Enchanted. It's commonly used as a substitute of the phrase "I miss you". The full lyrics are:
This is me praying that
This was the very first page
Not where the story line ends
My thoughts will echo your name, until I see you again
These are the words I held back, as I was leaving too soon.

Person A: timpttwtvfpnwtslemtweynuisyatatwihbaiwlts
Person B: me too 💜

timpttwtvfpnwtslemtweynuisyatatwihbaiwlts by All_too_bad(Taylor's Version) March 30, 2023