A friend sent me coins from his coinbase to mine using the QR code and no transa

[beamin]

and I never got the coins or even the message that I have got coins but they need to be verified.

My friend is a software engineer and quite tech savvy so I dont factor human error. Its been two days and I see no record of the coins. What do I do? He used an older address but I know all addresses generated are linked and new ones are just for privacy. My brother sent me coins the day before and they went through just fine.

[ranochigo]

Did your friend send you the coins using Coinbase's internal offchain transaction or on-chain transaction? Ask him if he could provide the TXID for the specific transaction.

It's highly likely a problem with coinbase and you should try contacting their support first.

[bob123]

My friend is a software engineer and quite tech savvy so I dont factor human error.

That's a mistake.
Just because he is a software engineer, this does not automatically mean that he actually knows how to use bitcoin.

You can't assume that someone is familiar with BTC just because his profession is IT-related.

Its been two days and I see no record of the coins. What do I do? He used an older address but I know all addresses generated are linked and new ones are just for privacy.

If old addresses stay valid and the transaction went through successfully (is it confirmed already? Check the transaction id.), then you need to contact the coinbase support.
The mempool is relatively clogged right now. Not that extreme that a 1 sat/vB transaction shouldn't be confirmed by now, but you'll never know. Maybe it didn't get broadcasted properly?

Definitely check the Transaction ID on a block explorer (or post it here).

My brother sent me coins the day before and they went through just fine.

Did both transactions have the same recipient address?