This issue is related to the amount of investment capital you have in the exchange. If you have an amount under $500 in the exchange but have several Traders 3+ active Wealthybot will not be able to open positions for all Traders. Please do one of the following to remedy this issue.
Use less Traders by deactivating the Traders that you would like to use less.
Add more investment capital to your exchange in USDT.
Enable "Average purchase amount" in each Trader you want to use and set it to a low number like 30. This will cause the Trader to make purchases at the low amount indicated.