I don't know the course.
We don't know the cause either - we are just other members, and don't have access to any restrictions on your account.
Restrictions may be applied by eBay, or by sellers. Sellers can, for example, block bids from any buyer who lives outside their delivery area, or has received more than one unpaid item strike in the last year.
eBay also enables sellers to block any buyer from bidding on their items, for any reason. eBay won't interfere in their decision. If it's a seller-applied restriction you can try contacting them to ask whether they will remove it, or add you to their exception list to allow you to bid. However, many sellers also block messages from blocked buyers, in which case there's nothing further you can do.
