NULV
Nuveen ESG Large-Cap Value ETF
stock BATS ETF

If you have a question about something unusual with a specific ETF you have to tell us what specific fund you are asking about.
UDI is a tiny ($3.52 million) fund - some individuals on reddit have portfolios larger than $3.52 million - that is "thinly traded"
https://www.investopedia.com/terms/t/thinly-traded.asp
That means there isn't much buying and selling of shares on a daily basis AKA low volume. The average daily volume of UDI for the past 10 days is only 1,036 shares per day. So you might not see any price action reported for UDI until later in the day because for the first hours of the trading day so few shares have been traded there is nothing to report.
For comparison the similar ESG ETF NULV the Nuveen ESG Large-Cap Value ETF has $2.19 *billion* in assets and 10-Day Average Volume of 75,286 shares.

If you have a question about something unusual with a specific ETF you have to tell us what specific fund you are asking about.
UDI is a tiny ($3.52 million) fund - some individuals on reddit have portfolios larger than $3.52 million - that is "thinly traded"
https://www.investopedia.com/terms/t/thinly-traded.asp
That means there isn't much buying and selling of shares on a daily basis AKA low volume. The average daily volume of UDI for the past 10 days is only 1,036 shares per day. So you might not see any price action reported for UDI until later in the day because for the first hours of the trading day so few shares have been traded there is nothing to report.
For comparison the similar ESG ETF NULV the Nuveen ESG Large-Cap Value ETF has $2.19 *billion* in assets and 10-Day Average Volume of 75,286 shares.