Isle of Man Transport says IT problems this week means some Go cards haven't topped up properly.
This morning on Facebook, the organisation says it's aware of problems with online payments over the last few days.
It says it's now working to solve the problem and has apologised for any inconvenience.
If you've paid for a top up which hasn't worked, you're being asked to email gocards@gov.im
Corporate income tax deadline looms
Dental and beauty clinic wants to expand
Could you help transform Manx healthcare?
New entries on Syrian sanctions list
Island company wants to import medical cannabis
Money laundering risks in insurance sector haven't changed
Interceltic Business Forum to visit Island for first time
Corporate tax return deadline nears