from the sounds of it you originally received a fixed charge notice (fcps) for "non display of valid insurance disc" which carries a fine which should have been paid within 56 days, the fine was not paid and a summons was issued. similar procedure to a parking ticket.
contact the garda and the garda can seek an adjournment to a suitable date if you are out of the country.
on court date explain to the judge the circumstances, if convicted likely outcome is a doubleing of original fine. no penalty points or disqualification for non display of valid insurance disc, penalty points and disqualification only relates to someone summonsed and convicted for offence of "no insurance"