In the journal website, there are table of contents available only from 1995-2019. Where can I find the table of contents before that? And, is the journal only offline through subscription? Thanks beforehand.
The tables of contents are not available online, but you can reconstruct them using Web of Science or MathSciNet (if you have access), or Google Scholar (query source:"Ars Combinatoria").
It should not be too much work to recreate the listings for all missing years; for starters, here I have listed the 764 papers from the years 1985-1994 (volumes 19 through 38).