All users, but particularly new users or users that have not been involved in many transactions lately, have limits on how much they can bid at any given time, both the total amount and the number of transactions.
See here for some very general info about limits:
https://www.ebay.com/help/buying/buying-limits/buying-restrictions?id=4012
Any time you place a bid on an auction, that amount counts toward your open transaction limit until the auction ends with another winner or else you win and pay. As you complete more purchases without problems, your limit will be raised. Linking a credit card or bank account to your PayPal account, and linking that to your eBay account can also raise your limit.
